From e054e13a5918cc9db523d649a3ccb98533de3ec6 Mon Sep 17 00:00:00 2001
From: lobo <andreas.dahm@gmail.com>
Date: Sun, 4 Oct 2026 10:43:02 +0200
Subject: [PATCH] feat(stats): add chart form selection and pie, donut, line
 charts

Tag rows with 0 games are no longer clickable.
---
 public/i18n/de.json                    |  10 ++
 public/i18n/en.json                    |  10 ++
 src/components/stats/ChartPicker.jsx   |  25 +++
 src/components/stats/FinishedStats.jsx |  31 ++--
 src/components/stats/PileTrend.jsx     |  22 ++-
 src/components/stats/PlatformStats.jsx |  18 ++-
 src/components/stats/SliceChart.jsx    |  76 +++++++++
 src/components/stats/StatsSection.jsx  |  16 +-
 src/components/stats/TasteStats.jsx    |  46 ++++--
 src/components/stats/TrendStats.jsx    |  12 +-
 src/components/stats/YearLine.jsx      |  48 ++++++
 src/components/stats/statGroupTile.jsx |  12 +-
 src/pages/Dashboard.jsx                |   2 +-
 src/pages/Dashboard.test.jsx           |  15 ++
 src/pages/PublicProfilePage.jsx        |   2 +-
 src/pages/PublicProfilePage.test.jsx   |  67 ++++++++
 src/pages/StatsPage.jsx                |  34 +++-
 src/pages/StatsPage.test.jsx           | 215 ++++++++++++++++++++++++-
 src/utils/statCharts.js                | 114 +++++++++++++
 src/utils/statCharts.test.js           |  94 +++++++++++
 src/utils/stats.js                     |   2 +-
 21 files changed, 815 insertions(+), 56 deletions(-)
 create mode 100644 src/components/stats/ChartPicker.jsx
 create mode 100644 src/components/stats/SliceChart.jsx
 create mode 100644 src/components/stats/YearLine.jsx
 create mode 100644 src/utils/statCharts.js
 create mode 100644 src/utils/statCharts.test.js

diff --git a/public/i18n/de.json b/public/i18n/de.json
index 899be1b..e69a44e 100644
--- a/public/i18n/de.json
+++ b/public/i18n/de.json
@@ -560,6 +560,16 @@
       "TURN_BASED_STRATEGY_TBS": "Rundenstrategie",
       "VISUAL_NOVEL": "Visual Novel"
     },
+    "CHART": {
+      "LABEL": "Diagramm",
+      "BARS": "Balken",
+      "PIE": "Torte",
+      "DONUT": "Ring",
+      "LINE": "Linie",
+      "LIST": "Liste",
+      "OTHER": "Andere",
+      "OVERLAP": "Anteil der Spiele, ein Spiel kann mehrfach zählen"
+    },
     "DRILL": {
       "SHOW_ALL": "Alle anzeigen",
       "LOAD_MORE": "Mehr laden",
diff --git a/public/i18n/en.json b/public/i18n/en.json
index 634686a..0b4ce0a 100644
--- a/public/i18n/en.json
+++ b/public/i18n/en.json
@@ -560,6 +560,16 @@
       "TURN_BASED_STRATEGY_TBS": "Turn-based strategy",
       "VISUAL_NOVEL": "Visual novel"
     },
+    "CHART": {
+      "LABEL": "Chart",
+      "BARS": "Bars",
+      "PIE": "Pie",
+      "DONUT": "Donut",
+      "LINE": "Line",
+      "LIST": "List",
+      "OTHER": "Other",
+      "OVERLAP": "Share of games, a game can count more than once"
+    },
     "DRILL": {
       "SHOW_ALL": "Show all",
       "LOAD_MORE": "Load more",
diff --git a/src/components/stats/ChartPicker.jsx b/src/components/stats/ChartPicker.jsx
new file mode 100644
index 0000000..ed55bc4
--- /dev/null
+++ b/src/components/stats/ChartPicker.jsx
@@ -0,0 +1,25 @@
+import {useTranslation} from 'react-i18next';
+
+import {Button} from '@/components/ui/button';
+import {STAT_CHARTS} from '../../utils/statCharts.js';
+
+/**
+ * The chart forms of a stat group as buttons.
+ *
+ * @param value the shown form
+ * @param onChange `(form)`
+ */
+export default function ChartPicker({group, value, onChange}) {
+    const {t} = useTranslation();
+    return (
+        <div role="group" aria-label={t('STATS.CHART.LABEL')} className="flex flex-wrap">
+            {STAT_CHARTS[group].map((form) => (
+                <Button key={form} variant={value === form ? 'secondary' : 'ghost'} size="sm"
+                        className="h-7 px-2 max-sm:min-h-11" aria-pressed={value === form}
+                        onClick={() => onChange(form)}>
+                    {t(`STATS.CHART.${form}`)}
+                </Button>
+            ))}
+        </div>
+    );
+}
diff --git a/src/components/stats/FinishedStats.jsx b/src/components/stats/FinishedStats.jsx
index f75e11b..9969f8f 100644
--- a/src/components/stats/FinishedStats.jsx
+++ b/src/components/stats/FinishedStats.jsx
@@ -2,12 +2,15 @@ import {useTranslation} from 'react-i18next';
 import {Flag} from 'lucide-react';
 
 import StatsSection from './StatsSection.jsx';
+import ChartPicker from './ChartPicker.jsx';
+import YearLine from './YearLine.jsx';
 import {DrillRow, StatCount, useStatDrill} from './StatDrill.jsx';
 
 /**
  * @param onSelect `(year)`: the rows are buttons
+ * @param bars false: a plain list, without the bars
  */
-export function YearBars({perYear, onSelect}) {
+export function YearBars({perYear, onSelect, bars = true}) {
     const max = Math.max(1, ...perYear.map((y) => y.games));
     return (
         <ul className="space-y-2">
@@ -15,10 +18,12 @@ export function YearBars({perYear, onSelect}) {
                 <li key={y.year} className="text-sm">
                     <DrillRow onSelect={onSelect && (() => onSelect(y.year))} className="flex items-center gap-3">
                         <span className="w-12 tabular-nums">{y.year}</span>
-                        <div className="h-2 flex-1 rounded-full bg-muted">
-                            <div className="h-full rounded-full bg-primary"
-                                 style={{width: `${(y.games / max) * 100}%`}}/>
-                        </div>
+                        {bars ? (
+                            <div className="h-2 flex-1 rounded-full bg-muted">
+                                <div className="h-full rounded-full bg-primary"
+                                     style={{width: `${(y.games / max) * 100}%`}}/>
+                            </div>
+                        ) : <span className="flex-1"/>}
                         <span className="w-8 text-right tabular-nums">{y.games}</span>
                     </DrillRow>
                 </li>
@@ -27,16 +32,24 @@ export function YearBars({perYear, onSelect}) {
     );
 }
 
-export default function FinishedStats({finished}) {
+/**
+ * @param chart BARS, LINE or LIST; a line needs two years, fewer draw the bars
+ * @param onChart `(form)`: shows the picker
+ */
+export default function FinishedStats({finished, chart = 'BARS', onChart}) {
     const {t} = useTranslation();
     const drill = useStatDrill();
+    const title = t('STATS.FINISHED.TITLE');
     return (
-        <StatsSection title={t('STATS.FINISHED.TITLE')} icon={Flag}>
+        <StatsSection title={title} icon={Flag}
+                      action={onChart && <ChartPicker group="FINISHED" value={chart} onChange={onChart}/>}>
             {finished.perYear.length === 0 ? (
                 <p className="text-sm text-muted-foreground">{t('STATS.FINISHED.EMPTY')}</p>
+            ) : chart === 'LINE' && finished.perYear.length >= 2 ? (
+                <YearLine perYear={finished.perYear} title={title}/>
             ) : (
-                <YearBars perYear={finished.perYear}
-                           onSelect={drill && ((year) => drill.open(`${t('STATS.FINISHED.TITLE')}: ${year}`, {key: 'FINISHED_YEAR', arg: year}))}/>
+                <YearBars perYear={finished.perYear} bars={chart !== 'LIST'}
+                          onSelect={drill && ((year) => drill.open(`${title}: ${year}`, {key: 'FINISHED_YEAR', arg: year}))}/>
             )}
             {finished.finishedBeforeTracking > 0 && (
                 <p className="text-xs text-muted-foreground">
diff --git a/src/components/stats/PileTrend.jsx b/src/components/stats/PileTrend.jsx
index 26a2bb4..d0367f5 100644
--- a/src/components/stats/PileTrend.jsx
+++ b/src/components/stats/PileTrend.jsx
@@ -2,6 +2,7 @@ import {useTranslation} from 'react-i18next';
 import {StatCount} from './StatDrill.jsx';
 import {formatDay} from '../../utils/format.js';
 import {trendPoints} from '../../utils/stats.js';
+import {trendBars} from '../../utils/statCharts.js';
 
 const WIDTH = 300;
 const HEIGHT = 60;
@@ -10,8 +11,9 @@ const HEIGHT = 60;
  * The pile size over the last 90 days and the moves of this month.
  *
  * @param trend the TREND group of GET /api/library/stats
+ * @param chart LINE or BARS; both are one click target, the days are not
  */
-export default function PileTrend({trend}) {
+export default function PileTrend({trend, chart = 'LINE'}) {
     const {t, i18n} = useTranslation();
     const {days, thisMonth} = trend;
     return (
@@ -32,10 +34,24 @@ export default function PileTrend({trend}) {
                                label={t('STATS.DRILL.TREND_MOVES')} className="flex w-full no-underline">
                         <svg viewBox={`0 0 ${WIDTH} ${HEIGHT}`} preserveAspectRatio="none" className="h-16 w-full"
                              role="img" aria-label={t('STATS.TREND.TITLE')}>
-                            <polyline data-testid="pile-trend" points={trendPoints(days, WIDTH, HEIGHT)} fill="none"
-                                      strokeWidth={2} vectorEffect="non-scaling-stroke" className="stroke-rose-500"/>
+                            {chart === 'BARS' ? trendBars(days, WIDTH, HEIGHT).map((bar) => (
+                                <rect key={bar.x} x={bar.x} y={bar.y} width={bar.w} height={bar.h} className="fill-rose-500"/>
+                            )) : (
+                                <polyline data-testid="pile-trend" points={trendPoints(days, WIDTH, HEIGHT)} fill="none"
+                                          strokeWidth={2} vectorEffect="non-scaling-stroke" className="stroke-rose-500"/>
+                            )}
                         </svg>
                     </StatCount>
+                    <table className="sr-only">
+                        <tbody>
+                            {days.map((d) => (
+                                <tr key={d.day}>
+                                    <td>{formatDay(d.day, i18n.language)}</td>
+                                    <td>{d.backlogGames}</td>
+                                </tr>
+                            ))}
+                        </tbody>
+                    </table>
                     <div className="mt-1 flex justify-between text-xs text-muted-foreground">
                         <span>{formatDay(days[0].day, i18n.language)}: {days[0].backlogGames}</span>
                         <span>{formatDay(days[days.length - 1].day, i18n.language)}: {days[days.length - 1].backlogGames}</span>
diff --git a/src/components/stats/PlatformStats.jsx b/src/components/stats/PlatformStats.jsx
index a73f8f2..e4d5d0f 100644
--- a/src/components/stats/PlatformStats.jsx
+++ b/src/components/stats/PlatformStats.jsx
@@ -2,18 +2,30 @@ import {useTranslation} from 'react-i18next';
 import {MonitorSmartphone} from 'lucide-react';
 
 import StatsSection from './StatsSection.jsx';
+import ChartPicker from './ChartPicker.jsx';
+import SliceChart from './SliceChart.jsx';
 import {TagBars} from './TasteStats.jsx';
 import {useTagDrill} from './StatDrill.jsx';
+import {topSlices} from '../../utils/statCharts.js';
 
-export default function PlatformStats({platforms}) {
+/**
+ * @param chart BARS, PIE, DONUT or LIST
+ * @param onChart `(form)`: shows the picker
+ */
+export default function PlatformStats({platforms, chart = 'BARS', onChart}) {
     const {t} = useTranslation();
     const select = useTagDrill();
+    const slices = chart === 'PIE' || chart === 'DONUT';
     return (
-        <StatsSection title={t('STATS.PLATFORMS.TITLE')} icon={MonitorSmartphone}>
+        <StatsSection title={t('STATS.PLATFORMS.TITLE')} icon={MonitorSmartphone}
+                      action={onChart && <ChartPicker group="PLATFORMS" value={chart} onChange={onChart}/>}>
             {platforms.perPlatform.length === 0 ? (
                 <p className="text-sm text-muted-foreground">{t('STATS.PLATFORMS.EMPTY')}</p>
+            ) : slices ? (
+                <SliceChart slices={topSlices(platforms.perPlatform, (p) => p.games)} donut={chart === 'DONUT'}
+                            drillKey="PLATFORM"/>
             ) : (
-                <TagBars tags={platforms.perPlatform} onSelect={select('PLATFORM')}/>
+                <TagBars tags={platforms.perPlatform} onSelect={select('PLATFORM')} bars={chart !== 'LIST'}/>
             )}
         </StatsSection>
     );
diff --git a/src/components/stats/SliceChart.jsx b/src/components/stats/SliceChart.jsx
new file mode 100644
index 0000000..1e12176
--- /dev/null
+++ b/src/components/stats/SliceChart.jsx
@@ -0,0 +1,76 @@
+import {useTranslation} from 'react-i18next';
+
+import {DrillRow, useDrillTarget} from './StatDrill.jsx';
+import {formatPlaytime} from '../../utils/games.js';
+import {slicePaths} from '../../utils/statCharts.js';
+
+const RADIUS = 50;
+const HOLE = 30;
+// Opacity steps of the accent, so every skin and dark mode work.
+const OPACITY = [1, 0.8, 0.62, 0.46, 0.32];
+
+const opacityOf = (slice, index) => (slice.other ? 1 : OPACITY[index] ?? 0.2);
+
+const useSliceTarget = (slice, drillKey, label) => useDrillTarget({
+    params: slice.other ? null : {key: drillKey, arg: slice.name},
+    title: slice.other ? '' : label(slice.name),
+    count: slice.value,
+});
+
+function SlicePath({slice, drillKey, label, d, index}) {
+    const target = useSliceTarget(slice, drillKey, label);
+    return (
+        <path d={d} fillRule="evenodd" onClick={target?.onClick}
+              className={`${slice.other ? 'fill-muted-foreground' : 'fill-primary'} stroke-card ${target ? 'cursor-pointer' : ''}`}
+              fillOpacity={opacityOf(slice, index)} strokeWidth={1.5}/>
+    );
+}
+
+function SliceRow({slice, drillKey, label, index}) {
+    const {t} = useTranslation();
+    const target = useSliceTarget(slice, drillKey, label);
+    const games = t('STATS.TASTE.GAMES', {count: slice.value});
+    return (
+        <li className="text-sm">
+            <DrillRow onSelect={target?.onClick} className="flex items-center gap-2">
+                <span className={`size-3 shrink-0 rounded-sm ${slice.other ? 'bg-muted-foreground' : 'bg-primary'}`}
+                      style={{opacity: opacityOf(slice, index)}}/>
+                <span className="min-w-0 flex-1 truncate">{slice.other ? t('STATS.CHART.OTHER') : label(slice.name)}</span>
+                <span className="ml-auto shrink-0 whitespace-nowrap text-muted-foreground tabular-nums">
+                    {slice.item ? `${formatPlaytime(slice.item.minutes)} · ${games}` : games}
+                </span>
+            </DrillRow>
+        </li>
+    );
+}
+
+/**
+ * A pie or donut with a legend. The legend rows do what the slices do, so the keyboard reaches every slice.
+ *
+ * @param slices from `topSlices`, sized by `value`
+ * @param drillKey the key of the games request; the slice name is its argument
+ * @param label shown name of a slice name
+ * @param note a line under the legend
+ */
+export default function SliceChart({slices, donut = false, drillKey, label = (name) => name, note}) {
+    const paths = slicePaths(slices.map((slice) => slice.value), RADIUS, donut ? HOLE : 0);
+    return (
+        <div className="@container space-y-2">
+            <div className="flex flex-col items-center gap-4 @sm:flex-row">
+                <svg viewBox={`0 0 ${2 * RADIUS} ${2 * RADIUS}`} aria-hidden="true" className="size-40 max-w-40 shrink-0">
+                    {slices.map((slice, index) => (
+                        <SlicePath key={slice.other ? 'other' : slice.name} slice={slice} drillKey={drillKey}
+                                   label={label} d={paths[index]} index={index}/>
+                    ))}
+                </svg>
+                <ul className="w-full min-w-0 flex-1 space-y-1">
+                    {slices.map((slice, index) => (
+                        <SliceRow key={slice.other ? 'other' : slice.name} slice={slice} drillKey={drillKey}
+                                  label={label} index={index}/>
+                    ))}
+                </ul>
+            </div>
+            {note && <p className="text-xs text-muted-foreground">{note}</p>}
+        </div>
+    );
+}
diff --git a/src/components/stats/StatsSection.jsx b/src/components/stats/StatsSection.jsx
index eff92e4..8556e1f 100644
--- a/src/components/stats/StatsSection.jsx
+++ b/src/components/stats/StatsSection.jsx
@@ -1,12 +1,18 @@
 import {Card} from '@/components/ui/card';
 
-export default function StatsSection({title, icon: Icon, children}) {
+/**
+ * @param action shown at the right of the title, e.g. a ChartPicker
+ */
+export default function StatsSection({title, icon: Icon, action, children}) {
     return (
         <Card className="gap-4 p-5">
-            <h2 className="flex items-center gap-2 font-semibold">
-                <Icon className="size-4 text-primary"/>
-                {title}
-            </h2>
+            <div className="flex flex-wrap items-center gap-2">
+                <h2 className="flex items-center gap-2 font-semibold">
+                    <Icon className="size-4 text-primary"/>
+                    {title}
+                </h2>
+                {action && <div className="ml-auto font-normal">{action}</div>}
+            </div>
             {children}
         </Card>
     );
diff --git a/src/components/stats/TasteStats.jsx b/src/components/stats/TasteStats.jsx
index 2d289ce..6da1626 100644
--- a/src/components/stats/TasteStats.jsx
+++ b/src/components/stats/TasteStats.jsx
@@ -2,31 +2,37 @@ import {useTranslation} from 'react-i18next';
 import {Palette} from 'lucide-react';
 
 import StatsSection from './StatsSection.jsx';
+import ChartPicker from './ChartPicker.jsx';
+import SliceChart from './SliceChart.jsx';
 import {DrillRow, useTagDrill} from './StatDrill.jsx';
 import {formatPlaytime} from '../../utils/games.js';
 import {genreKey} from '../../utils/stats.js';
+import {topSlices} from '../../utils/statCharts.js';
 
 /**
- * @param onSelect `(tag, shownLabel)`: the rows are buttons
+ * @param onSelect `(tag, shownLabel)`: the rows are buttons, except a row with 0 games
+ * @param bars false: a plain list, without the bars
  */
-export function TagBars({tags, label = (name) => name, onSelect}) {
+export function TagBars({tags, label = (name) => name, onSelect, bars = true}) {
     const {t} = useTranslation();
     const max = Math.max(1, ...tags.map((tag) => tag.minutes));
     return (
         <ul className="space-y-2">
             {tags.map((tag) => (
                 <li key={tag.name} className="text-sm">
-                    <DrillRow onSelect={onSelect && (() => onSelect(tag, label(tag.name)))}>
+                    <DrillRow onSelect={onSelect && tag.games > 0 && (() => onSelect(tag, label(tag.name)))}>
                         <div className="flex justify-between gap-2">
                             <span className="truncate">{label(tag.name)}</span>
                             <span className="text-muted-foreground tabular-nums">
                                 {formatPlaytime(tag.minutes)} · {t('STATS.TASTE.GAMES', {count: tag.games})}
                             </span>
                         </div>
-                        <div className="mt-1 h-1.5 rounded-full bg-muted">
-                            <div className="h-full rounded-full bg-primary"
-                                 style={{width: `${Math.max(2, (tag.minutes / max) * 100)}%`}}/>
-                        </div>
+                        {bars && (
+                            <div className="mt-1 h-1.5 rounded-full bg-muted">
+                                <div className="h-full rounded-full bg-primary"
+                                     style={{width: `${Math.max(2, (tag.minutes / max) * 100)}%`}}/>
+                            </div>
+                        )}
                     </DrillRow>
                 </li>
             ))}
@@ -34,27 +40,41 @@ export function TagBars({tags, label = (name) => name, onSelect}) {
     );
 }
 
-export default function TasteStats({taste}) {
+/**
+ * @param chart BARS, PIE, DONUT or LIST; the pie and donut size a slice by games, and a game can count in several
+ * @param onChart `(form)`: shows the picker
+ */
+export default function TasteStats({taste, chart = 'BARS', onChart}) {
     const {t} = useTranslation();
     const select = useTagDrill();
+    const action = onChart && <ChartPicker group="TASTE" value={chart} onChange={onChart}/>;
     if (taste.genres.length === 0 && taste.moods.length === 0) {
         return (
-            <StatsSection title={t('STATS.TASTE.TITLE')} icon={Palette}>
+            <StatsSection title={t('STATS.TASTE.TITLE')} icon={Palette} action={action}>
                 <p className="text-sm text-muted-foreground">{t('STATS.TASTE.EMPTY')}</p>
             </StatsSection>
         );
     }
+    const tagChart = (tags, drillKey, label) => {
+        if (chart !== 'PIE' && chart !== 'DONUT') {
+            return <TagBars tags={tags} onSelect={select(drillKey)} label={label} bars={chart !== 'LIST'}/>;
+        }
+        const slices = topSlices(tags, (tag) => tag.games);
+        return slices.length > 0 && (
+            <SliceChart slices={slices} donut={chart === 'DONUT'} drillKey={drillKey} label={label}
+                        note={t('STATS.CHART.OVERLAP')}/>
+        );
+    };
     return (
-        <StatsSection title={t('STATS.TASTE.TITLE')} icon={Palette}>
+        <StatsSection title={t('STATS.TASTE.TITLE')} icon={Palette} action={action}>
             <div className="grid gap-6 sm:grid-cols-2">
                 <div className="space-y-2">
                     <span className="text-sm font-medium">{t('STATS.TASTE.GENRES')}</span>
-                    <TagBars tags={taste.genres} onSelect={select('GENRE')}
-                             label={(name) => t(`STATS.GENRE.${genreKey(name)}`, {defaultValue: name})}/>
+                    {tagChart(taste.genres, 'GENRE', (name) => t(`STATS.GENRE.${genreKey(name)}`, {defaultValue: name}))}
                 </div>
                 <div className="space-y-2">
                     <span className="text-sm font-medium">{t('STATS.TASTE.MOODS')}</span>
-                    <TagBars tags={taste.moods} onSelect={select('MOOD')} label={(name) => t(`PLAY_NEXT.MOOD.${name}`, {defaultValue: name})}/>
+                    {tagChart(taste.moods, 'MOOD', (name) => t(`PLAY_NEXT.MOOD.${name}`, {defaultValue: name}))}
                 </div>
             </div>
         </StatsSection>
diff --git a/src/components/stats/TrendStats.jsx b/src/components/stats/TrendStats.jsx
index 1dfa954..ba16b03 100644
--- a/src/components/stats/TrendStats.jsx
+++ b/src/components/stats/TrendStats.jsx
@@ -2,13 +2,19 @@ import {useTranslation} from 'react-i18next';
 import {TrendingDown} from 'lucide-react';
 
 import StatsSection from './StatsSection.jsx';
+import ChartPicker from './ChartPicker.jsx';
 import PileTrend from './PileTrend.jsx';
 
-export default function TrendStats({trend}) {
+/**
+ * @param chart LINE or BARS
+ * @param onChart `(form)`: shows the picker
+ */
+export default function TrendStats({trend, chart = 'LINE', onChart}) {
     const {t} = useTranslation();
     return (
-        <StatsSection title={t('STATS.TREND.TITLE')} icon={TrendingDown}>
-            <PileTrend trend={trend}/>
+        <StatsSection title={t('STATS.TREND.TITLE')} icon={TrendingDown}
+                      action={onChart && <ChartPicker group="TREND" value={chart} onChange={onChart}/>}>
+            <PileTrend trend={trend} chart={chart}/>
         </StatsSection>
     );
 }
diff --git a/src/components/stats/YearLine.jsx b/src/components/stats/YearLine.jsx
new file mode 100644
index 0000000..402a8fe
--- /dev/null
+++ b/src/components/stats/YearLine.jsx
@@ -0,0 +1,48 @@
+import {useTranslation} from 'react-i18next';
+
+import {StatCount, useDrillTarget} from './StatDrill.jsx';
+import {linePoints, yearSeries} from '../../utils/statCharts.js';
+
+const WIDTH = 300;
+const HEIGHT = 80;
+
+function YearPoint({point, year, games, title}) {
+    const target = useDrillTarget({params: {key: 'FINISHED_YEAR', arg: year}, title: `${title}: ${year}`, count: games});
+    return (
+        <circle cx={point.x} cy={point.y} r={4} onClick={target?.onClick}
+                className={`fill-primary stroke-card ${target ? 'cursor-pointer' : ''}`} strokeWidth={1.5}/>
+    );
+}
+
+/**
+ * Finished games per year as a line. The year labels under it do what the points do.
+ *
+ * @param perYear `[{year, games}]`
+ * @param title the group title, the start of the dialog title
+ */
+export default function YearLine({perYear, title}) {
+    const {t} = useTranslation();
+    const series = yearSeries(perYear);
+    const points = linePoints(series.map((y) => y.games), WIDTH, HEIGHT);
+    return (
+        <div className="space-y-2">
+            <svg viewBox={`-8 -8 ${WIDTH + 16} ${HEIGHT + 16}`} aria-hidden="true" className="h-24 w-full">
+                <polyline points={points.map((p) => `${p.x},${p.y}`).join(' ')} fill="none" strokeWidth={2}
+                          className="stroke-primary" strokeLinejoin="round"/>
+                {series.map((y, i) => (
+                    <YearPoint key={y.year} point={points[i]} year={y.year} games={y.games} title={title}/>
+                ))}
+            </svg>
+            <ul className="flex flex-wrap justify-between gap-x-3 gap-y-1 text-xs tabular-nums">
+                {series.map((y) => (
+                    <li key={y.year}>
+                        <StatCount params={{key: 'FINISHED_YEAR', arg: y.year}} count={y.games} title={`${title}: ${y.year}`}
+                                   label={`${y.year}: ${t('STATS.TASTE.GAMES', {count: y.games})}`}>
+                            {y.year}: {y.games}
+                        </StatCount>
+                    </li>
+                ))}
+            </ul>
+        </div>
+    );
+}
diff --git a/src/components/stats/statGroupTile.jsx b/src/components/stats/statGroupTile.jsx
index fb011b4..d1b99ed 100644
--- a/src/components/stats/statGroupTile.jsx
+++ b/src/components/stats/statGroupTile.jsx
@@ -6,6 +6,7 @@ import TasteStats from './TasteStats.jsx';
 import HabitsStats from './HabitsStats.jsx';
 import FinishedStats from './FinishedStats.jsx';
 import PlatformStats from './PlatformStats.jsx';
+import {chartOf} from '../../utils/statCharts.js';
 
 /**
  * One stat group as a tile; null while its data is not there. A function, not a component: a tile grid leaves out a
@@ -13,17 +14,18 @@ import PlatformStats from './PlatformStats.jsx';
  *
  * @param stats the answer of GET /api/library/stats, or the stats of a public profile
  * @param linked true for the user's own games: the dashboard and the owner on the profile
+ * @param charts the chart form per group of the user whose stats these are
  */
-export default function statGroupTile(id, stats, linked = true) {
+export default function statGroupTile(id, stats, linked = true, charts = null) {
     switch (id) {
         case 'STATS_OVERVIEW': return stats?.overview ? <OverviewStats overview={stats.overview}/> : null;
         case 'STATS_PILE': return stats?.pile ? <PileStats pile={stats.pile} linked={linked}/> : null;
-        case 'STATS_TREND': return stats?.trend ? <TrendStats trend={stats.trend}/> : null;
+        case 'STATS_TREND': return stats?.trend ? <TrendStats trend={stats.trend} chart={chartOf(charts, 'TREND')}/> : null;
         case 'STATS_TOP_GAMES': return stats?.topGames ? <TopGamesStats topGames={stats.topGames} linked={linked}/> : null;
-        case 'STATS_TASTE': return stats?.taste ? <TasteStats taste={stats.taste}/> : null;
+        case 'STATS_TASTE': return stats?.taste ? <TasteStats taste={stats.taste} chart={chartOf(charts, 'TASTE')}/> : null;
         case 'STATS_HABITS': return stats?.habits ? <HabitsStats habits={stats.habits}/> : null;
-        case 'STATS_FINISHED': return stats?.finished ? <FinishedStats finished={stats.finished}/> : null;
-        case 'STATS_PLATFORMS': return stats?.platforms ? <PlatformStats platforms={stats.platforms}/> : null;
+        case 'STATS_FINISHED': return stats?.finished ? <FinishedStats finished={stats.finished} chart={chartOf(charts, 'FINISHED')}/> : null;
+        case 'STATS_PLATFORMS': return stats?.platforms ? <PlatformStats platforms={stats.platforms} chart={chartOf(charts, 'PLATFORMS')}/> : null;
         default: return null;
     }
 }
diff --git a/src/pages/Dashboard.jsx b/src/pages/Dashboard.jsx
index 382b545..ba4163d 100644
--- a/src/pages/Dashboard.jsx
+++ b/src/pages/Dashboard.jsx
@@ -118,7 +118,7 @@ const Dashboard = () => {
                 );
             case 'ACTIVITY': return hasSteamId && activity && <ActivityCard activity={activity}/>;
             case 'ACHIEVEMENTS': return hasSteamId && achievements && <AchievementsCard summary={achievements}/>;
-            default: return statGroupTile(id, stats.stats);
+            default: return statGroupTile(id, stats.stats, true, userData?.settings?.statCharts);
         }
     };
 
diff --git a/src/pages/Dashboard.test.jsx b/src/pages/Dashboard.test.jsx
index a05b6de..3310e99 100644
--- a/src/pages/Dashboard.test.jsx
+++ b/src/pages/Dashboard.test.jsx
@@ -96,6 +96,21 @@ describe('Dashboard', () => {
         expect(fetch).toHaveBeenCalledWith(expect.stringMatching(/\/api\/library\/stats\?groups=HABITS,TREND$/), expect.anything());
     });
 
+    it('showsAStatTileInTheChartFormOfTheUser', async () => {
+        fetchRoutes({
+            ...dashboardRoutes({dashboardTiles: [{id: 'STATS_FINISHED', size: 'M'}], statCharts: {FINISHED: 'LINE'}}),
+            'GET /api/library/stats': json(200, {trend: null, finished: {finishedBeforeTracking: 0,
+                perYear: [{year: 2022, games: 3}, {year: 2024, games: 1}]}}),
+        });
+        renderDashboard();
+
+        expect(await screen.findByRole('button', {name: /2022/})).toBeTruthy();
+        expect(screen.getByRole('button', {name: /2024/})).toBeTruthy();
+        expect(screen.getByText('2023: 0')).toBeTruthy();
+        expect(screen.queryByRole('button', {name: /2023/})).toBeNull();
+        expect(screen.queryByRole('group', {name: 'STATS.CHART.LABEL'})).toBeNull();
+    });
+
     it('leaves out a stat tile whose data did not come', async () => {
         const container = mockDashboard({dashboardTiles: [{id: 'STATS_PILE', size: 'M'}, {id: 'MOST_PLAYED', size: 'M'}]});
 
diff --git a/src/pages/PublicProfilePage.jsx b/src/pages/PublicProfilePage.jsx
index 293f82b..42a0a50 100644
--- a/src/pages/PublicProfilePage.jsx
+++ b/src/pages/PublicProfilePage.jsx
@@ -138,7 +138,7 @@ export default function PublicProfilePage() {
                     && <Playing games={library.playing.slice(0, PLAYING_GAMES[size])} compact={size === 'S'}/>;
             case 'FINISHED':
                 return library.finished?.length > 0 && <Finished games={library.finished.slice(0, FINISHED_GAMES[size])} equipped={equipped}/>;
-            default: return statGroupTile(id, library.stats, owner);
+            default: return statGroupTile(id, library.stats, owner, profile.style?.statCharts);
         }
     };
     // Core sends only the data of the shown tiles (the ticket says which), so a new tile needs a new load.
diff --git a/src/pages/PublicProfilePage.test.jsx b/src/pages/PublicProfilePage.test.jsx
index 7eab23e..37d6250 100644
--- a/src/pages/PublicProfilePage.test.jsx
+++ b/src/pages/PublicProfilePage.test.jsx
@@ -339,6 +339,73 @@ describe('PublicProfilePage', () => {
         }
     });
 
+    const platformStats = {pile: null, trend: null, taste: null, finished: null, habits: null, topGames: null,
+        platforms: {perPlatform: [{name: 'Steam', games: 10, minutes: 5000}, {name: 'PS5', games: 2, minutes: 600}]}};
+    const platformTile = {tiles: [{id: 'STATS_PLATFORMS', size: 'M'}]};
+    const platformGames = {'GET /api/public/profiles/library/stats/games': json(200, {
+        content: [{appid: 7, name: 'Hades', status: 'BACKLOG', playtimeMinutes: 0}], page: 0, size: 40, totalElements: 1, totalPages: 1})};
+
+    it('showsTheOwnerChartFormWithoutAPicker', async () => {
+        library.stats = platformStats;
+        try {
+            mockBackends({style: {...platformTile, statCharts: {PLATFORMS: 'DONUT'}}});
+            const {container} = renderPage();
+
+            expect(await screen.findByText('Steam')).toBeTruthy();
+            expect(container.querySelectorAll('path.stroke-card')).toHaveLength(2);
+            expect(screen.queryByRole('group', {name: 'STATS.CHART.LABEL'})).toBeNull();
+        } finally {
+            delete library.stats;
+        }
+    });
+
+    it('showsBarsForAFormTheProfileDoesNotKnow', async () => {
+        library.stats = platformStats;
+        try {
+            mockBackends({style: {...platformTile, statCharts: {PLATFORMS: 'RADAR'}}});
+            const {container} = renderPage();
+
+            expect(await screen.findByText('Steam')).toBeTruthy();
+            expect(container.querySelector('path.stroke-card')).toBeNull();
+        } finally {
+            delete library.stats;
+        }
+    });
+
+    it('aChartLegendRowOfTheOwnerOpensTheDetailPage', async () => {
+        localStorage.setItem('tbp_session', '1');
+        library.stats = platformStats;
+        try {
+            mockBackends({me: {displayName: 'lobo', role: 'USER'}, style: {...platformTile, statCharts: {PLATFORMS: 'PIE'}},
+                extra: platformGames});
+            const {container} = renderPage();
+
+            await waitFor(() => expect(container.querySelectorAll('path.stroke-card')).toHaveLength(2));
+            fireEvent.click(await screen.findByRole('button', {name: /Steam/}));
+
+            expect((await screen.findByRole('link', {name: /Hades/})).getAttribute('href')).toBe('/library/7');
+        } finally {
+            delete library.stats;
+            localStorage.clear();
+        }
+    });
+
+    it('aChartLegendRowOfAVisitorShowsAPlainGameRow', async () => {
+        library.stats = platformStats;
+        try {
+            mockBackends({style: {...platformTile, statCharts: {PLATFORMS: 'PIE'}}, extra: platformGames});
+            const {container} = renderPage();
+
+            await waitFor(() => expect(container.querySelectorAll('path.stroke-card')).toHaveLength(2));
+            fireEvent.click(await screen.findByRole('button', {name: /Steam/}));
+
+            expect(await screen.findByText('Hades')).toBeTruthy();
+            expect(screen.queryByRole('link', {name: /Hades/})).toBeNull();
+        } finally {
+            delete library.stats;
+        }
+    });
+
     it('opensTheGamesBehindPerfectGames', async () => {
         library.perfectGames = 12;
         library.averageCompletion = 64.5;
diff --git a/src/pages/StatsPage.jsx b/src/pages/StatsPage.jsx
index 0fc3877..6608a2f 100644
--- a/src/pages/StatsPage.jsx
+++ b/src/pages/StatsPage.jsx
@@ -1,3 +1,4 @@
+import {useRef} from 'react';
 import {useTranslation} from 'react-i18next';
 import {RefreshCw} from 'lucide-react';
 
@@ -14,12 +15,37 @@ import FinishedStats from '../components/stats/FinishedStats.jsx';
 import PlatformStats from '../components/stats/PlatformStats.jsx';
 import {StatDrillProvider} from '../components/stats/StatDrill.jsx';
 import useUserStats from '../hooks/useUserStats.js';
+import useSaveResponse from '../hooks/useSaveResponse.js';
+import {useCurrentUserContext} from '../context/CurrentUserContext.jsx';
+import {chartOf, saveStatChart, STAT_CHARTS} from '../utils/statCharts.js';
 
 const ALL_GROUPS = [];
 
 export default function StatsPage() {
     const {t} = useTranslation();
     const {stats, failed, reload} = useUserStats(ALL_GROUPS);
+    const {user, updateUser} = useCurrentUserContext();
+    const runSave = useSaveResponse();
+    const charts = user?.settings?.statCharts;
+
+    // The new form shows at once; a failed save puts only this group back.
+    const setChart = (group, form) => updateUser((u) => {
+        const next = {...u.settings?.statCharts};
+        if (form) next[group] = form;
+        else delete next[group];
+        return {...u, settings: {...u.settings, statCharts: next}};
+    });
+    const latest = useRef({});
+    const change = async (group, form) => {
+        const before = charts?.[group] ?? null;
+        const sent = form === STAT_CHARTS[group][0] ? null : form;
+        const id = (latest.current[group] ?? 0) + 1;
+        latest.current[group] = id;
+        setChart(group, sent);
+        // A failed older save must not undo a newer choice.
+        if (!await runSave(() => saveStatChart(group, sent)) && latest.current[group] === id) setChart(group, before);
+    };
+    const chartProps = (group) => ({chart: chartOf(charts, group), onChart: (form) => change(group, form)});
 
     return (
         <StatDrillProvider source="own">
@@ -47,12 +73,12 @@ export default function StatsPage() {
                     <div className="grid gap-6 md:grid-cols-2">
                         <div className="md:col-span-2"><OverviewStats overview={stats.overview}/></div>
                         <PileStats pile={stats.pile}/>
-                        <TrendStats trend={stats.trend}/>
+                        <TrendStats trend={stats.trend} {...chartProps('TREND')}/>
                         <TopGamesStats topGames={stats.topGames}/>
-                        <TasteStats taste={stats.taste}/>
-                        <PlatformStats platforms={stats.platforms}/>
+                        <TasteStats taste={stats.taste} {...chartProps('TASTE')}/>
+                        <PlatformStats platforms={stats.platforms} {...chartProps('PLATFORMS')}/>
                         <HabitsStats habits={stats.habits}/>
-                        <FinishedStats finished={stats.finished}/>
+                        <FinishedStats finished={stats.finished} {...chartProps('FINISHED')}/>
                     </div>
                 )}
             </PageContainer>
diff --git a/src/pages/StatsPage.test.jsx b/src/pages/StatsPage.test.jsx
index edbf40b..c0dc982 100644
--- a/src/pages/StatsPage.test.jsx
+++ b/src/pages/StatsPage.test.jsx
@@ -1,14 +1,18 @@
 // @vitest-environment jsdom
 import {afterEach, beforeEach, describe, expect, it, vi} from 'vitest';
-import {cleanup, fireEvent, render, screen, waitFor} from '@testing-library/react';
-import {MemoryRouter} from 'react-router-dom';
+import {cleanup, fireEvent, screen, waitFor, within} from '@testing-library/react';
 import StatsPage from './StatsPage.jsx';
-import {PreferencesProvider} from '../context/PreferencesContext.jsx';
+import {renderWithProviders} from '../test/renderWithProviders.jsx';
 import {fetchRoutes, json} from '../test/fetchRoutes.js';
 
 vi.mock('react-i18next', () => import('../test/i18n-mock.js'));
 
-const answerStats = (answer) => fetchRoutes({'GET /api/library/stats': answer});
+const me = (statCharts) => json(200, {email: 'a@b.de', settings: {statCharts}});
+const answerStats = (answer, statCharts) => fetchRoutes({
+    'GET /api/library/stats': answer,
+    'GET /api/users/me': me(statCharts),
+    'PUT /api/users/settings/stat-chart': json(204, {}),
+});
 
 const stats = (extra = {}) => ({
     overview: {totalGames: 12, totalPlaytimeMinutes: 6000, playedGames: 8, neverStarted: 4,
@@ -27,7 +31,7 @@ const stats = (extra = {}) => ({
     ...extra,
 });
 
-const renderPage = () => render(<MemoryRouter><PreferencesProvider><StatsPage/></PreferencesProvider></MemoryRouter>);
+const renderPage = () => renderWithProviders(<StatsPage/>);
 
 describe('StatsPage', () => {
     beforeEach(() => {
@@ -44,8 +48,9 @@ describe('StatsPage', () => {
         renderPage();
 
         expect(await screen.findByText('STATS.OVERVIEW.TITLE')).toBeTruthy();
-        expect(fetch).toHaveBeenCalledOnce();
-        expect(fetch.mock.calls[0][0]).toMatch(/\/api\/library\/stats$/);
+        const statsCalls = fetch.mock.calls.filter(([url]) => url.includes('/api/library/stats'));
+        expect(statsCalls).toHaveLength(1);
+        expect(statsCalls[0][0]).toMatch(/\/api\/library\/stats$/);
         for (const title of ['PILE', 'TREND', 'TOP_GAMES', 'TASTE', 'HABITS', 'FINISHED', 'PLATFORMS']) {
             expect(screen.getByText(`STATS.${title}.TITLE`)).toBeTruthy();
         }
@@ -87,12 +92,13 @@ describe('StatsPage', () => {
 
         fireEvent.click(await screen.findByRole('button', {name: /DASHBOARD.RETRY/}));
 
-        await waitFor(() => expect(fetch).toHaveBeenCalledTimes(2));
+        await waitFor(() => expect(fetch.mock.calls.filter(([url]) => url.includes('/api/library/stats'))).toHaveLength(2));
     });
 
     it('opensTheGamesBehindARowWithTheRawName', async () => {
         fetchRoutes({
             'GET /api/library/stats': json(200, stats()),
+            'GET /api/users/me': me(),
             'GET /api/library/stats/games': json(200, {content: [{appid: 620, name: 'Portal 2', status: 'BACKLOG', playtimeMinutes: 60}],
                 page: 0, size: 40, totalElements: 1, totalPages: 1}),
         });
@@ -149,4 +155,197 @@ describe('StatsPage', () => {
 
         expect(screen.queryByRole('button', {name: /STATS.HABITS.MOON/})).toBeNull();
     });
+
+    describe('chart forms', () => {
+        const section = (title) => screen.getByText(title).closest('[data-slot="card"]');
+        const picker = (title) => within(section(title)).getByRole('group', {name: 'STATS.CHART.LABEL'});
+        const putBodies = () => fetch.mock.calls.filter(([, init]) => init?.method === 'PUT').map(([, init]) => JSON.parse(init.body));
+        const slices = (title) => section(title).querySelectorAll('path.stroke-card');
+
+        it('showsBarsAsTodayAndAPickerPerChartableGroup', async () => {
+            answerStats(json(200, stats()));
+            renderPage();
+
+            await screen.findByText('STATS.PLATFORMS.TITLE');
+
+            expect(slices('STATS.PLATFORMS.TITLE')).toHaveLength(0);
+            for (const title of ['PLATFORMS', 'TASTE', 'FINISHED', 'TREND']) {
+                expect(within(picker(`STATS.${title}.TITLE`)).getAllByRole('button').length).toBeGreaterThan(1);
+            }
+            expect(within(section('STATS.TOP_GAMES.TITLE')).queryByRole('group', {name: 'STATS.CHART.LABEL'})).toBeNull();
+            expect(within(picker('STATS.PLATFORMS.TITLE')).getByRole('button', {name: 'STATS.CHART.BARS'}).getAttribute('aria-pressed')).toBe('true');
+        });
+
+        it('savesThePickedFormAndSavesNullForTheDefault', async () => {
+            answerStats(json(200, stats()));
+            renderPage();
+            await screen.findByText('STATS.PLATFORMS.TITLE');
+
+            fireEvent.click(within(picker('STATS.PLATFORMS.TITLE')).getByRole('button', {name: 'STATS.CHART.PIE'}));
+
+            await waitFor(() => expect(slices('STATS.PLATFORMS.TITLE')).toHaveLength(2));
+            expect(putBodies()).toEqual([{group: 'PLATFORMS', chart: 'PIE'}]);
+
+            fireEvent.click(within(picker('STATS.PLATFORMS.TITLE')).getByRole('button', {name: 'STATS.CHART.BARS'}));
+
+            await waitFor(() => expect(slices('STATS.PLATFORMS.TITLE')).toHaveLength(0));
+            expect(putBodies().at(-1)).toEqual({group: 'PLATFORMS', chart: null});
+        });
+
+        it('showsTheStoredFormOfTheUser', async () => {
+            answerStats(json(200, stats()), {PLATFORMS: 'DONUT', TREND: 'BARS'});
+            renderPage();
+
+            await waitFor(() => expect(slices('STATS.PLATFORMS.TITLE')).toHaveLength(2));
+            expect(screen.queryByTestId('pile-trend')).toBeNull();
+        });
+
+        it('putsTheOldFormBackWhenTheSaveFails', async () => {
+            fetchRoutes({
+                'GET /api/library/stats': json(200, stats()),
+                'GET /api/users/me': me(),
+                'PUT /api/users/settings/stat-chart': json(500, {}),
+            });
+            renderPage();
+            await screen.findByText('STATS.PLATFORMS.TITLE');
+
+            fireEvent.click(within(picker('STATS.PLATFORMS.TITLE')).getByRole('button', {name: 'STATS.CHART.PIE'}));
+
+            await waitFor(() => expect(putBodies()).toHaveLength(1));
+            await waitFor(() => expect(slices('STATS.PLATFORMS.TITLE')).toHaveLength(0));
+            expect(within(picker('STATS.PLATFORMS.TITLE')).getByRole('button', {name: 'STATS.CHART.BARS'}).getAttribute('aria-pressed')).toBe('true');
+        });
+
+        it('aLegendRowOpensTheGamesWithThePlatform', async () => {
+            fetchRoutes({
+                'GET /api/library/stats': json(200, stats()),
+                'GET /api/users/me': me({PLATFORMS: 'PIE'}),
+                'GET /api/library/stats/games': json(200, {content: [], page: 0, size: 40, totalElements: 0, totalPages: 0}),
+            });
+            renderPage();
+
+            await waitFor(() => expect(slices('STATS.PLATFORMS.TITLE')).toHaveLength(2));
+            fireEvent.click(await within(section('STATS.PLATFORMS.TITLE')).findByRole('button', {name: /PS5/}));
+
+            expect(await screen.findByRole('dialog')).toBeTruthy();
+            await waitFor(() => expect(fetch.mock.calls.at(-1)[0]).toMatch(/stats\/games\?key=PLATFORM&arg=PS5&page=0$/));
+        });
+
+        it('theOtherSliceIsNotAButtonAndHoldsTheRest', async () => {
+            const perPlatform = Array.from({length: 8}, (_, i) => ({name: `P${i}`, games: 8 - i, minutes: 10}));
+            answerStats(json(200, stats({platforms: {perPlatform}})), {PLATFORMS: 'PIE'});
+            renderPage();
+
+            await waitFor(() => expect(slices('STATS.PLATFORMS.TITLE')).toHaveLength(6));
+            const legend = within(section('STATS.PLATFORMS.TITLE'));
+            expect(legend.getAllByRole('button', {name: /P\d/})).toHaveLength(5);
+            expect(legend.getByText('STATS.CHART.OTHER').closest('button')).toBeNull();
+            expect(legend.getByText('STATS.TASTE.GAMES:6')).toBeTruthy();
+        });
+
+        it('aPlatformRowWithoutGamesIsNoButtonInBarsAndList', async () => {
+            const perPlatform = [{name: 'Steam', games: 3, minutes: 5}, {name: 'Switch', games: 0, minutes: 0}];
+            for (const form of ['BARS', 'LIST']) {
+                answerStats(json(200, stats({platforms: {perPlatform}})), {PLATFORMS: form});
+                renderPage();
+
+                const platforms = within(await screen.findByText('STATS.PLATFORMS.TITLE').then(() => section('STATS.PLATFORMS.TITLE')));
+                expect(platforms.getByRole('button', {name: /Steam/})).toBeTruthy();
+                expect(platforms.getByText('Switch')).toBeTruthy();
+                expect(platforms.queryByRole('button', {name: /Switch/})).toBeNull();
+                cleanup();
+            }
+        });
+
+        it('aPlatformWithoutGamesGetsNoSlice', async () => {
+            answerStats(json(200, stats({platforms: {perPlatform: [
+                {name: 'Steam', games: 3, minutes: 5}, {name: 'Switch', games: 0, minutes: 0}]}})), {PLATFORMS: 'PIE'});
+            renderPage();
+
+            await waitFor(() => expect(slices('STATS.PLATFORMS.TITLE')).toHaveLength(1));
+            expect(within(section('STATS.PLATFORMS.TITLE')).queryByText('Switch')).toBeNull();
+        });
+
+        it('showsTheEmptyTextForEveryForm', async () => {
+            answerStats(json(200, stats({platforms: {perPlatform: []}})), {PLATFORMS: 'PIE'});
+            renderPage();
+
+            expect(await screen.findByText('STATS.PLATFORMS.EMPTY')).toBeTruthy();
+        });
+
+        it('aLineYearOpensItsGamesAndAYearWithoutGamesIsNoButton', async () => {
+            fetchRoutes({
+                'GET /api/library/stats': json(200, stats({finished: {finishedBeforeTracking: 0,
+                    perYear: [{year: 2022, games: 3}, {year: 2024, games: 1}]}})),
+                'GET /api/users/me': me({FINISHED: 'LINE'}),
+                'GET /api/library/stats/games': json(200, {content: [], page: 0, size: 40, totalElements: 0, totalPages: 0}),
+            });
+            renderPage();
+
+            const finished = within(await screen.findByText('STATS.FINISHED.TITLE').then(() => section('STATS.FINISHED.TITLE')));
+            await waitFor(() => expect(finished.getByRole('button', {name: /2022/})).toBeTruthy());
+            expect(finished.getByRole('button', {name: /2024/})).toBeTruthy();
+            expect(finished.queryByRole('button', {name: /2023/})).toBeNull();
+            expect(finished.getByText('2023: 0')).toBeTruthy();
+            const circles = [...section('STATS.FINISHED.TITLE').querySelectorAll('circle')];
+            expect(circles).toHaveLength(3);
+            expect(circles.filter((c) => c.getAttribute('class').includes('cursor-pointer'))).toHaveLength(2);
+
+            fireEvent.click(finished.getByRole('button', {name: /2022/}));
+
+            await waitFor(() => expect(fetch.mock.calls.at(-1)[0]).toMatch(/stats\/games\?key=FINISHED_YEAR&arg=2022&page=0$/));
+        });
+
+        it('aLineWithOneYearDrawsBars', async () => {
+            answerStats(json(200, stats()), {FINISHED: 'LINE'});
+            renderPage();
+
+            const finished = within(await screen.findByText('STATS.FINISHED.TITLE').then(() => section('STATS.FINISHED.TITLE')));
+            await waitFor(() => expect(finished.getByRole('button', {name: /2026/})).toBeTruthy());
+            expect(section('STATS.FINISHED.TITLE').querySelector('polyline')).toBeNull();
+        });
+
+        it('aDonutOfTheTasteOpensTheGenreWithItsRawNameAndShowsTheOverlapNote', async () => {
+            fetchRoutes({
+                'GET /api/library/stats': json(200, stats()),
+                'GET /api/users/me': me({TASTE: 'DONUT'}),
+                'GET /api/library/stats/games': json(200, {content: [], page: 0, size: 40, totalElements: 0, totalPages: 0}),
+            });
+            renderPage();
+
+            const taste = within(await screen.findByText('STATS.TASTE.TITLE').then(() => section('STATS.TASTE.TITLE')));
+            await waitFor(() => expect(taste.getAllByText('STATS.CHART.OVERLAP')).toHaveLength(2));
+            fireEvent.click(taste.getByRole('button', {name: /STATS\.GENRE/}));
+
+            await waitFor(() => expect(fetch.mock.calls.at(-1)[0]).toMatch(/stats\/games\?key=GENRE&arg=Shooter&page=0$/));
+        });
+
+        it('theTrendBarsStayOneClickTargetWithAListOfTheDays', async () => {
+            answerStats(json(200, stats()), {TREND: 'BARS'});
+            renderPage();
+
+            const trend = within(await screen.findByText('STATS.TREND.TITLE').then(() => section('STATS.TREND.TITLE')));
+            await waitFor(() => expect(section('STATS.TREND.TITLE').querySelectorAll('rect')).toHaveLength(2));
+            expect(trend.getAllByRole('button', {name: 'STATS.DRILL.TREND_MOVES'})).toHaveLength(1);
+            expect(section('STATS.TREND.TITLE').querySelectorAll('table tr')).toHaveLength(2);
+        });
+
+        // REVIEW-FINDING: the picker buttons sit inside the h2, so the heading name becomes "title + Chart Bars Pie ..."
+        it('reviewFinding_thePickerIsNotPartOfTheHeadingName', async () => {
+            answerStats(json(200, stats()));
+            renderPage();
+
+            expect(await screen.findByRole('heading', {name: 'STATS.PLATFORMS.TITLE'})).toBeTruthy();
+        });
+
+        // REVIEW-FINDING: an empty tag list in pie/donut form draws an empty chart box and the overlap note
+        it('reviewFinding_anEmptyMoodListInThePieShowsNoChartAndNoNote', async () => {
+            answerStats(json(200, stats({taste: {genres: [{name: 'Shooter', games: 2, minutes: 1200}], moods: []}})),
+                {TASTE: 'PIE'});
+            renderPage();
+
+            await waitFor(() => expect(slices('STATS.TASTE.TITLE')).toHaveLength(1));
+            expect(within(section('STATS.TASTE.TITLE')).getAllByText('STATS.CHART.OVERLAP')).toHaveLength(1);
+        });
+    });
 });
diff --git a/src/utils/statCharts.js b/src/utils/statCharts.js
new file mode 100644
index 0000000..aeaec90
--- /dev/null
+++ b/src/utils/statCharts.js
@@ -0,0 +1,114 @@
+import {apiFetch} from './api.js';
+import {dayNumber} from './stats.js';
+
+// The chart forms of each stat group, the first is the default. Auth checks the same list.
+export const STAT_CHARTS = {
+    PLATFORMS: ['BARS', 'PIE', 'DONUT', 'LIST'],
+    TASTE: ['BARS', 'PIE', 'DONUT', 'LIST'],
+    FINISHED: ['BARS', 'LINE', 'LIST'],
+    TREND: ['LINE', 'BARS'],
+};
+
+/**
+ * The chart form to draw: the stored one when the group offers it, else the group's default.
+ *
+ * @param charts group -> form, as the user settings hold it; may be missing
+ */
+export const chartOf = (charts, group) => {
+    const forms = STAT_CHARTS[group];
+    const stored = charts?.[group];
+    return forms.includes(stored) ? stored : forms[0];
+};
+
+/**
+ * The slices of a pie: the items with a value, biggest first. More than `keep + 1` items: the `keep` biggest and
+ * one "other" slice with the rest.
+ *
+ * @returns `[{name, value, item, other}]`; the other slice has no name and no item
+ */
+export const topSlices = (items, valueOf, keep = 5) => {
+    const slices = items
+        .map((item) => ({name: item.name, value: valueOf(item), item, other: false}))
+        .filter((slice) => slice.value > 0)
+        .sort((a, b) => b.value - a.value);
+    if (slices.length <= keep + 1) return slices;
+    const rest = slices.slice(keep).reduce((sum, slice) => sum + slice.value, 0);
+    return [...slices.slice(0, keep), {name: null, value: rest, item: null, other: true}];
+};
+
+const round = (n) => Math.round(n * 1000) / 1000;
+
+/**
+ * SVG path data of the slices of a pie (`inner` 0) or a donut, in a square of `2 * radius`, the first slice at the
+ * top, clockwise. A slice that is the whole circle is drawn as two half arcs.
+ */
+export const slicePaths = (values, radius, inner = 0) => {
+    const total = values.reduce((sum, value) => sum + value, 0);
+    const point = (angle, r) => `${round(radius + r * Math.sin(angle))},${round(radius - r * Math.cos(angle))}`;
+    let start = 0;
+    return values.map((value) => {
+        if (value <= 0) return '';
+        const from = start;
+        start += value;
+        if (value === total) {
+            const ring = (r, sweep) => `M${radius},${radius - r} A${r},${r} 0 1 ${sweep} ${radius},${radius + r} A${r},${r} 0 1 ${sweep} ${radius},${radius - r} Z`;
+            return inner > 0 ? `${ring(radius, 1)} ${ring(inner, 0)}` : ring(radius, 1);
+        }
+        const a0 = (from / total) * 2 * Math.PI;
+        const a1 = (start / total) * 2 * Math.PI;
+        const large = a1 - a0 > Math.PI ? 1 : 0;
+        const outer = `A${radius},${radius} 0 ${large} 1 ${point(a1, radius)}`;
+        return inner > 0
+            ? `M${point(a0, radius)} ${outer} L${point(a1, inner)} A${inner},${inner} 0 ${large} 0 ${point(a0, inner)} Z`
+            : `M${radius},${radius} L${point(a0, radius)} ${outer} Z`;
+    });
+};
+
+/**
+ * The years from the first to the last one, a year without games has 0.
+ *
+ * @param perYear `[{year, games}]`
+ */
+export const yearSeries = (perYear) => {
+    if (perYear.length === 0) return [];
+    const years = perYear.map((y) => y.year);
+    const first = Math.min(...years);
+    const games = new Map(perYear.map((y) => [y.year, y.games]));
+    return Array.from({length: Math.max(...years) - first + 1},
+        (_, i) => ({year: first + i, games: games.get(first + i) ?? 0}));
+};
+
+/**
+ * Points of a line chart, spread over the width; the y axis starts at 0, so a small change looks small.
+ */
+export const linePoints = (values, width, height) => {
+    const max = Math.max(1, ...values);
+    return values.map((value, i) => ({
+        x: (i / (values.length - 1)) * width,
+        y: height - (value / max) * height,
+    }));
+};
+
+/**
+ * Bars for the pile per day, like trendPoints: x follows the date, so days without a snapshot keep their width.
+ */
+export const trendBars = (days, width, height) => {
+    if (days.length === 0) return [];
+    const max = Math.max(1, ...days.map((d) => d.backlogGames));
+    const first = dayNumber(days[0].day);
+    const slot = width / (dayNumber(days[days.length - 1].day) - first + 1);
+    return days.map((d) => {
+        const h = (d.backlogGames / max) * height;
+        return {x: (dayNumber(d.day) - first) * slot, y: height - h, w: slot * 0.8, h};
+    });
+};
+
+/**
+ * @param chart null puts the group back to its default form
+ */
+export const saveStatChart = (group, chart) =>
+    apiFetch(`${import.meta.env.VITE_API_URL}/api/users/settings/stat-chart`, {
+        method: 'PUT',
+        headers: {'Content-Type': 'application/json'},
+        body: JSON.stringify({group, chart}),
+    });
diff --git a/src/utils/statCharts.test.js b/src/utils/statCharts.test.js
new file mode 100644
index 0000000..4dc6083
--- /dev/null
+++ b/src/utils/statCharts.test.js
@@ -0,0 +1,94 @@
+import {describe, expect, it} from 'vitest';
+import {chartOf, linePoints, slicePaths, topSlices, trendBars, yearSeries} from './statCharts.js';
+
+describe('chartOf', () => {
+    it('gives the stored form of the group', () => {
+        expect(chartOf({PLATFORMS: 'PIE'}, 'PLATFORMS')).toBe('PIE');
+    });
+
+    it('falls back to the first form', () => {
+        expect(chartOf({}, 'PLATFORMS')).toBe('BARS');
+        expect(chartOf({}, 'TREND')).toBe('LINE');
+        expect(chartOf({TASTE: 'LINE'}, 'TASTE')).toBe('BARS');
+        expect(chartOf({PLATFORMS: 'RADAR'}, 'PLATFORMS')).toBe('BARS');
+    });
+
+    it('accepts a missing or odd settings value', () => {
+        for (const charts of [null, undefined, 'PIE', 5]) expect(chartOf(charts, 'FINISHED')).toBe('BARS');
+    });
+});
+
+describe('topSlices', () => {
+    const item = (name, games) => ({name, games});
+    const games = (i) => i.games;
+
+    it('keeps all items up to one more than keep, biggest first', () => {
+        const slices = topSlices([1, 2, 3, 4, 5, 6].map((n) => item(`P${n}`, n)), games);
+        expect(slices.map((s) => s.name)).toEqual(['P6', 'P5', 'P4', 'P3', 'P2', 'P1']);
+        expect(slices.some((s) => s.other)).toBe(false);
+    });
+
+    it('sums the rest into an other slice', () => {
+        const slices = topSlices([1, 2, 3, 4, 5, 6, 7, 8].map((n) => item(`P${n}`, n)), games);
+        expect(slices).toHaveLength(6);
+        expect(slices.slice(0, 5).map((s) => s.name)).toEqual(['P8', 'P7', 'P6', 'P5', 'P4']);
+        expect(slices[5]).toMatchObject({name: null, other: true, value: 3 + 2 + 1, item: null});
+    });
+
+    it('drops items without a value', () => {
+        expect(topSlices([item('A', 2), item('B', 0)], games).map((s) => s.name)).toEqual(['A']);
+    });
+});
+
+describe('slicePaths', () => {
+    it('draws one value as a full circle, not an empty arc', () => {
+        const [d] = slicePaths([4], 50, 0);
+        expect(d).toBe('M50,0 A50,50 0 1 1 50,100 A50,50 0 1 1 50,0 Z');
+    });
+
+    it('draws one value of a donut as a ring with a hole', () => {
+        const [d] = slicePaths([4], 50, 30);
+        expect(d.match(/M/g)).toHaveLength(2);
+    });
+
+    it('splits a circle in the order of the values, the first from the top', () => {
+        const [a, b] = slicePaths([1, 1], 50, 0);
+        expect(a).toBe('M50,50 L50,0 A50,50 0 0 1 50,100 Z');
+        expect(b).toBe('M50,50 L50,100 A50,50 0 0 1 50,0 Z');
+    });
+
+    it('gives a donut slice an inner arc', () => {
+        const [a] = slicePaths([1, 3], 50, 30);
+        expect(a).toContain('A30,30 0 0 0');
+    });
+});
+
+describe('yearSeries', () => {
+    it('fills the years between the first and the last with 0', () => {
+        expect(yearSeries([{year: 2024, games: 1}, {year: 2022, games: 3}]))
+            .toEqual([{year: 2022, games: 3}, {year: 2023, games: 0}, {year: 2024, games: 1}]);
+        expect(yearSeries([])).toEqual([]);
+    });
+});
+
+describe('linePoints', () => {
+    it('spreads the values over the width, the biggest at the top', () => {
+        expect(linePoints([2, 4, 0], 100, 40)).toEqual([{x: 0, y: 20}, {x: 50, y: 0}, {x: 100, y: 40}]);
+    });
+});
+
+describe('trendBars', () => {
+    const day = (date, backlogGames) => ({day: date, backlogGames});
+
+    it('puts each bar where its date is, a day without a snapshot keeps its width', () => {
+        const bars = trendBars([day('2026-09-01', 10), day('2026-09-02', 5), day('2026-09-05', 0)], 100, 40);
+        expect(bars.map((b) => b.x)).toEqual([0, 20, 80]);
+        expect(bars.map((b) => b.h)).toEqual([40, 20, 0]);
+        expect(bars[1].y).toBe(20);
+    });
+
+    it('draws a single day', () => {
+        expect(trendBars([day('2026-09-01', 3)], 100, 40)).toHaveLength(1);
+        expect(trendBars([], 100, 40)).toEqual([]);
+    });
+});
diff --git a/src/utils/stats.js b/src/utils/stats.js
index 8903231..96b63d1 100644
--- a/src/utils/stats.js
+++ b/src/utils/stats.js
@@ -19,7 +19,7 @@ export const formatPercent = (share, locale) =>
     share.toLocaleString(locale, {style: 'percent', maximumFractionDigits: 0});
 
 const DAY_MS = 24 * 60 * 60 * 1000;
-const dayNumber = (day) => Math.round(Date.parse(`${day}T00:00:00Z`) / DAY_MS);
+export const dayNumber = (day) => Math.round(Date.parse(`${day}T00:00:00Z`) / DAY_MS);
 
 /**
  * Points of an SVG polyline for the pile per day, oldest left. x follows the date, so days without a snapshot