feat(effects): polish 8 effects and add 7 new engines with parallax

Synthwave, fireflies, snow, sakura, nebula: CSS/SVG. Matrix and
constellation: canvas. Existing engines gain depth, color, glow, and
parallax (mouse and device tilt, opt-in on iOS)

README.md

@@ -33,11 +33,11 @@ To Be Played is split into three repositories:
   trips to the moon, the longest gaming day, games started but under one hour; finished games per year; games per platform.
 - **Pile Points** (`/points`): points for playing games off your pile (start, finish by time to beat, 100 %, month and
   streak bonuses; Core checks proof of play), spent in a small shop on an avatar border, a badge, a premium accent, a
-  banner frame, an effect for 100 % games and an animated page or banner background (CSS and SVG, in `effects.css`),
+  banner frame, an effect for 100 % games and an animated page or banner background (CSS and SVG in `effects.css`, two canvas engines in `EffectCanvas`; layers follow the mouse and the phone tilt, on iPhone after the switch in the settings),
   shown on the dashboard and the public profile. Twelve more items are unlock-only: they show locked with a progress bar
   until a goal is reached (games finished, 100 % games, weeks in a row, months with a smaller pile, months with more
   play time). Skins (`skins.css`, Pastel, Retro CRT, Cyberpunk bought, Steam unlocked) are full themes made of CSS
-  variables; a skin wins over accent and corners, while badges, borders, frames and effects stay on top. The balance is in the header. Every effect stands still with the
+  variables; a skin wins over accent and corners, while badges, borders, frames and effects stay on top. The balance is in the header. Every effect stands still (canvas: one static frame, no loop) with the
   system setting "reduce motion" or the "Reduce animations" switch in the settings.
 - **Landing page**: next to the community numbers and the top games, three blocks: games per platform, top genres and
   finished games per year of all users.