Logic at 60fps, sprites at 8–12fps. 12 is the pixel-art sweet spot; 18+ reads rushed, ≤6 reads idle. Never tie hitboxes to render framerate.
Vary rate per clip: idle 4–8fps, walk 8–10, run/attacks up to 15–20.
Uneven timing for attacks: slow anticipation (~120–200ms/frame), near-instant strike (1–2 frames at ~30–60ms, one may be a smear), moderate recovery (~80–150ms). Even timing for cycles (walk ~80–150ms/frame, run ~50–80ms). In Phaser use per-frame duration overrides, not one global frameRate, for non-cycles. Aseprite-authored sheets: keep the exported per-frame durations verbatim and set no frameRate — hand-guessed fps ran 40–120% fast. Never pass duration to play() (freezes on frame 1); retime with anims.timeScale.
Slow in, slow out: cluster spacing at a pose's start/end, big jump mid-motion. Five frames = small, small, HUGE, small, small.
Hold the follow-through pose a beat longer; overshoot past rest on fast moves, then settle.
Loops must not double the contact pose at the seam. Watch every loop for 10 straight seconds before calling it done.

Frame budgets (small sprites)

Clip	Frames	Notes
Idle	2–4	1px breathing bob; move interior pixels/hair, not the silhouette
Walk	4–8	4 = two contacts + two passing; cut "up/recoil" frames first
Run	6 (4 tiny, 3 with extreme poses)	not a fast walk: airborne moments, lean, arm swing
Jump	3–5 phases	crouch → stretch ascent → apex → fall → land squash; select by velocity, not a timed clip
Attack	3–8	1–3 anticipation, 1–2 strike, 1–3 recovery
Hit react	1–3	one strong recoil pose + white flash beats three soft poses
Death	4–6	one-shot, ends on a settled pose
FX (slash/smoke)	3–6	expand → disperse → fade; can run 15–24fps

(Shipped reference points: Celeste runs on 4 frames, Shovel Knight walks on 6.) AI-generated sheets: cut down to these budgets — delete near-duplicates first; redundancy reads as floatiness.

The gameplay/animation contract

Responsiveness vs weight is a contract, not a contest: put the weight in follow-through and recovery, which don't delay input.

Player attacks: short startup (~2–5 logic frames for light moves), compensating with exaggerated poses and smears. Long windups are a deliberate cost for heavies only.
Enemy attacks invert it: long, silhouette-distinct telegraphs that show an attack is coming AND where it lands. The anticipation pose is gameplay information.
Fast transition into the strike reads as MORE powerful — power is contrast in spacing, not duration. Slow windups convey weakness.
Cancel windows: dodge/move/next-attack may interrupt startup and recovery; only active frames are committed (the Dead Cells trick).
Never look idle before you can act: hold the recovery pose, then pop to idle — the sprite is the UI for vulnerability state.
Movement animation never gates movement. Velocity changes instantly; the run cycle starts mid-stride.
Drive animation FROM state: pick jump/fall frames by velocity, trigger land-squash from the collision event. Never setTimeout gameplay to clip length. On interrupt (hit mid-attack), cut instantly to the hit reaction — never finish the old clip.
Give control back during follow-through: the player moves while cloth/hair finish their arcs.
Damage lands on the contact frame, measured per clip. For authored sheets, find the strike frame in each attack clip (bone track / the frame the blade crosses the target line) and time the hit to it; retimed variants keep windup → [0, a0], strike = [a0, a1], held recovery after. A uniform tempo-stretch of an attack clip is never the answer — it lands damage 300–700 ms before the blade shows. When a boss shares an atlas with variants, keep its authored telegraph timings; only the variants retime.

Readability at small sizes

Silhouette test: idle, walk, anticipation, attack must be distinguishable as pure black shapes. If not, redraw the pose — don't add frames.
One smear frame for any fast arc: stretch the weapon/limb into a blur covering the path, 1 frame at ~30–60ms. The smear can visually carry the hitbox.
Exaggerate past reality: extend limbs on the strike, squash 1–2px on landings/hits. At 16–32px, realistic motion reads as nothing.
Keep arcs: hands/feet/weapon tips trace curves across frames — overlay the frames and check; zigzags only as deliberate snap accents.
Pixel hygiene on AI frames: consistent palette across frames, no swimming outline pixels, constant volumes (head mass shouldn't pulse), feet pinned to one baseline.

Secondary motion & life

Hair/cape/scarf lag the body by 1 frame and settle 1–2 frames after it stops — the cheapest way to make a 4-frame loop feel alive.
Sub-pixel animation for motion under one pixel: animate the anti-aliasing shades inside the sprite instead of moving the silhouette. Best for idles, faces, small objects.
Idle personality: blinks every few seconds, hair sway — secondary elements, not whole-body motion.
Transitions last: idle↔walk snaps fine at 8–12fps; spend frames only on land-squash and attack-recovery-pop. Add dedicated transitions only where the snap visibly jars.
The one transition always worth it: the pivot. A single 1-frame turn pose shown on direction change (and a lean/head-turn on wall-slide) is the highest life-per-frame purchase in the sheet — direction flips without it are where "stiff" reads come from.

Review checklist

Silhouette test passes for idle/walk/anticipation/attack?
No player attack delays its hit >~100ms after input unless deliberately heavy?
Every enemy attack telegraphed by a distinct readable pose?
Strikes are 1–2 fast frames with a smear; anticipation/recovery hold longer?
Recovery cancelable; sprite never looks idle before control returns?
All loops seamless — no doubled seam frame, no baseline bob?
Hair/cloth lags one frame and settles after the body?
Feet planted — stride matches move speed, no moonwalking?
Palette/outline/volume consistent across frames (no AI shimmer)?
Land/hit squash triggered by the game event, not the clip timeline?
Hitboxes on 60Hz timers, sprites at 8–15fps — decoupled?
Watched each clip 10s straight — idle still alive, run still energetic?

Related skills: pixel-art / animated-spritesheets (generate the frames), vfx (effects animation), game-feel (hit stop, squash from code), phaser (animation API).

animation

Animation craft

Timing & spacing