2D VFX (Visual Effects)

VFX = the small effects that make actions feel impactful: hit flashes, explosion frames, smoke puffs, screen shake. The "juice" of game feel.

Reference: Vlambeer's "The Art of Screenshake" (talk by Jan Willem Nijman, 2013) — the canonical breakdown of game-feel techniques. Every indie should watch.

Canonical effect frame counts

Effect              Frames   FPS    Total      Notes
Smoke puff          6-8      8-12   600-700ms  Expand → drift → fade
Fire (loop)         4-6      8-10   400-500ms  Turbulent loop, no hard end
Water splash        5-7      ad-hoc 200-400ms  Impact + arc + settle
Electricity         2-3      24-30  60-100ms   Fast jitter, looping
Sparks              3-5      30-60  50-150ms   Quick, small
Sword swing trail   3-4      24+    100-150ms  One-shot, fades quick
Damage flash        2-3      ad-hoc 60-120ms   Stuck on hit moment
Explosion           8-12     8-15   500-1000ms Bright peak, smoke residual
Heal / buff burst   6-8      8-12   500-700ms  Soft expand
Power-up pickup     8-10     12-15  500-700ms  Sparkle + shimmer

Smoke

Canonical 6-frame smoke puff:

F1: small dark cloud (initial)
F2: expanded, lighter
F3: maximum size, mid-tone
F4: drifting up, fading
F5: thin, mostly dispersed
F6: barely visible, last wisp

Color: starts dark (impact dust), goes lighter (warm air), ends near sky color. Use 3-color palette ramp.

For LOOPING smoke (chimney): 4-6 frame loop, drift up offset by 1-2 px per frame, opacity stays roughly constant.

Fire

Looping fire is noisy and turbulent. Hard to make periodic without visible repetition. Tricks:

Long loop (6+ frames) with subtle frame-to-frame change.
Multiple flame sprites at slight offsets, layered.
Vertical scroll of internal flame "noise" texture (shader trick).

Color ramp for fire:

Base = dark red (#3a0a00).
Mid = orange (#d04a00).
Top = yellow (#fae670).
Smoke trail above = gray (#666).

Cooler for magical fire: cyan core + purple outer.

Water splash

Splash on impact:

F1: vertical jet (water displaced upward)
F2: peak height, droplets separating
F3: droplets in arc, base ring forming
F4: droplets falling back, ring expanding
F5: most water settled, ripple ring
F6: ripple fading

Water palette: blue ramp + white highlights at impact peak.

Looping water (puddle ripple, river): 3-4 frame loop with shifted highlight pattern. Subtle.

Electricity

Electric/lightning bolts: 2-3 frames, played FAST (24-30 fps), jitter between similar shapes. The eye sees "alive electricity" rather than discrete frames.

Tricks:

3 frame loop with slightly different bolt shape each frame.
Intentional asymmetry — never mirror perfectly.
Use yellow + cyan + white for color contrast.
Add subtle glow halo (semi-transparent yellow circle behind bolt).

Continuous beam: same approach but bolt path is a steady curve, jitter is in branches.

Hitstop / hit pause

Brief game-time freeze on hit. Critical for game feel.

Light hit:    1-2 frames freeze (~16-33ms)
Medium hit:   3-5 frames (~50-80ms)
Heavy hit:    6-10 frames (~100-167ms)
Crit / parry: 8-15 frames (~133-250ms) + visual flourish

During freeze:

All gameplay paused (player can still move? OPTIONAL — usually no).
Particle effects continue (smoke, sparks).
Screen shake fires.
Color flash on hit sprite (full white or palette flash).

Implementation: Time.timeScale = 0.05 for X frames in Unity, or manual game-state pause flag. Don't actually Time.timeScale = 0 — breaks animation timing on resume.

Screen shake

Random offset to camera position over short duration.

Intensity curves

Linear decay: intensity * (1 - t / duration). OK but mechanical.
Quadratic decay: intensity * (1 - t / duration)^2. Snappier.
Bounce: oscillating, decaying envelope.

Shake parameters

Magnitude: pixels of offset. 1-3 px = subtle hit, 4-8 px = explosion, 10+ px = boss / earthquake.
Frequency: shakes per second. 30+ Hz feels chaotic, 15 Hz feels rhythmic.
Duration: 100-300ms typical for hits, 500-1000ms for explosions.

Direction

Random 2D: omni-directional shake.
Directional (along hit normal): more grounded, shows attack direction.

Cinemachine 2D in Unity has built-in Impulse system. Cinemachine Impulse Source on the trigger, listener on the camera, takes care of decay

multiple sources.

Color flash

Sprite turns full white (or another color) for 1-3 frames on hit. Communicates "I got hit" without animation work.

Implementation: shader uniform _FlashColor with alpha 0..1. Lerp from white (1) to no-flash (0) over the flash duration.

Trail effects

For sword swings, projectiles, dashing:

Pre-baked trail sprite

1-frame curved line drawn through the swing arc. Cheap, looks consistent.

Frame-stripe trail

Stack semi-transparent copies of the sprite at offset positions over the last N frames. Engine-side. Looks dynamic, pixel-perfect difficult.

Shader ribbon

Procedural geometry along the swing path. More common in higher-res 2D.

Particles (procedural)

When pre-baked frames don't suffice (large numbers, varied behavior):

Unity Particle System (yes, works for 2D — set Renderer module to Sprite, set Y-axis billboard).
Godot CPUParticles2D / GPUParticles2D.
Custom sprite-pool emitter.

Procedural is right for:

Many small particles (debris, dust, splatter).
Variable lifetime / spawn count (heal sparkles, depending on amount healed).
Physics-driven (debris bouncing on terrain).

Pre-baked is right for:

Distinctive shapes (specific spell effect).
Tightly choreographed (boss attack with exact pattern).

Decals / aftermath

Persistent marks: scorch marks, blood splatters, footprints, cracks.

Spawn as sprite at hit location.
Random rotation + small scale variance.
Optional fade over N seconds OR persist until scene cleanup.
Limit total count (object pool, oldest fades first).

Juice principles ("Art of Screenshake" summary)

For every meaningful action, layer:

Squash-stretch on sprite (subtle pixel deform).
Hitstop on impact.
Color flash on the affected sprite.
Particle burst at impact.
Screen shake scaled to action weight.
Sound with attack envelope (omitted in art skill, but listed for completeness).
Trail if motion has direction.
Decal if persistent.

Subtle layering of all = "juicy" feel. Single technique applied = falls flat. Test by toggling each layer off and feeling the loss.

Common bugs

Particles in pixel art at non-integer positions: shimmer / blur. Solution: snap particle positions to integer.
Hitstop too long: feels frozen, not impactful. Tune to ≤80ms for light, ≤160ms heavy.
Screen shake too aggressive: nausea-inducing. Magnitude < 8 px typical.
No color flash on hit: hits feel unregistered.
Smoke puff endless: forgot the fade-out frames. End on alpha=0.
Fire loop visibly periodic: extend loop length, vary frames more.

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