t1k-designer-base-feel-juice

name	t1k:designer:base:feel-juice
description	Game feel and juice — screen shake, hit stop, particles, animation curves, input responsiveness, feedback timing. Makes actions feel satisfying.
effort	high
context	fork
keywords	["juice","screen shake","hit stop","hit-stop","particles","particle burst","animation curves","easing","squash stretch","coyote time","camera punch","time slow","chromatic aberration","vignette","hit flash","damage numbers","knockback"]
version	1.12.0
origin	theonekit-designer
repository	The1Studio/theonekit-designer
module	base
protected	false

Game Feel & Juice

When This Skill Triggers

• Making combat, movement, or UI interactions feel more satisfying
• Adding screen shake, hit stop (freeze frames), or camera punch
• Designing floating damage numbers, hit flash, or particle bursts
• Tuning animation easing curves (ease-out, spring, squash-and-stretch)
• Fixing input latency, input buffering, or dead zone issues
• Adding time-slow (bullet time), chromatic aberration, or vignette effects

Core Concepts

Juice = visual + audio feedback that makes every action feel consequential. Rule: Every player action must produce visible, audible feedback within 1 frame.

Feedback Priority Stack (when budget is limited)

1. Sound (always — even at 8-bit fidelity)
2. Hit flash / color change (1-2 frames)
3. Particle burst (3-10 particles minimum)
4. Camera reaction (shake or punch)
5. Screen-space effect (chromatic aberration, time slow)

Screen Shake Parameters

Scenario	Amplitude	Frequency	Decay
Light hit	0.05–0.10	20–30 Hz	Exponential 0.15s
Heavy hit	0.15–0.30	15–20 Hz	Exponential 0.25s
Explosion	0.40–0.60	10–15 Hz	Linear 0.4s
Boss slam	0.80–1.00	8–12 Hz	Ease-out 0.6s

Implementation: use a camera shake component on a singleton; a shake system reads amplitude/frequency/decay and drives the camera offset each frame. Never shake the main camera directly — shake a child rig.

Hit Stop / Time Freeze

• Per-entity freeze (preferred): pause simulation for 2–4 frames via your engine's time-scale or system group API. Resume via countdown component.
• Global time scale: simpler but breaks UI animations — use only for boss cinematic moments.
• Values: light hit = 2 frames; heavy hit = 3–4 frames; parry/crit = 5–6 frames.
• Freeze attacker AND target — asymmetric freeze causes visual disconnect.

Particle Burst Patterns

Event	Count	Speed	Lifetime	Shape
On-hit (light)	5–8 sparks	2–4 m/s	0.2–0.3s	Hemisphere toward attacker
On-hit (heavy)	12–20 shards	4–8 m/s	0.3–0.5s	Full sphere + ground splat
On-death	20–40 mixed	3–10 m/s	0.5–1.0s	Radial burst + linger
On-level-up	15–25 sparkles	1–3 m/s upward	1.0–2.0s	Cone upward

Use GPU-instanced particle bursts. Attach to entities via your engine's event/component system.

Audio Feedback Timing

Phase	Timing	Notes
Attack wind-up	Frame 0 (input frame)	Whoosh/grunt starts immediately
Impact	Frame of collision	Crack/thud on hit confirm
Cooldown tick	Every 0.25s remaining	Subtle UI blip — not every frame
Critical hit	+50ms delay after impact	Stinger layered on top of impact sfx

Rule: audio cue starts on the same frame as the visual — never let visual lead audio by >1 frame.

Mobile Haptic Feedback Patterns

• Light tap (UI button, collect item): HapticFeedback.LightImpact()
• Medium impact (enemy hit, block): HapticFeedback.MediumImpact()
• Heavy impact (death, boss hit, explosion): HapticFeedback.HeavyImpact()
• Selection change (menu scroll): HapticFeedback.SelectionChanged()
• Pattern: visual → audio → haptic (50ms max delay between layers)
• Always provide haptic toggle in settings; default ON for mobile, OFF for tablet.

Quick Reference

Effect	Values	Reference
Hit stop	2-4 frames at 60fps (33-66ms)	references/hit-feedback.md
Screen shake	magnitude 0.1-0.3 (hit), 0.5+ (explosion)	references/screen-effects.md
Ease-out appear	0.2s UI elements	references/animation-curves.md
Input latency budget	<100ms total, <50ms action games	references/input-responsiveness.md
Coyote time	3-6 frames grace after leaving edge	references/input-responsiveness.md
Input buffer window	2-4 frames before action completes	references/input-responsiveness.md

Gotchas

#	Anti-Pattern	Problem	Fix
1	No feedback on actions	Feels broken, unresponsive	Every action: sound + visual within 1 frame
2	Delayed input response	Player feels lag, distrusted	Start animation on input frame (optimistic rendering)
3	Excessive shake	Nauseating, unplayable for some	Cap magnitude at 0.5 units; add reduce-motion option
4	Uniform feedback	All hits feel the same	Scale effects by damage: crit = 2× shake + larger number
5	No squash/stretch	Motion feels rigid, lifeless	Apply 0.8/1.2 scale on land/impact over 0.2s
6	Missing coyote time	Platformer feels unfair	Always: 3-6 frame jump grace after leaving platform
7	Shake in large-scale battles	500+ units = constant max-trauma, camera never stops vibrating	Disable CinemachineImpulseListener on camera or set CameraTrauma.MaxIntensity=0. Trauma-per-hit (0.03) × hundreds of hits/frame = instant saturation

Cross-References

• game-feel-foundations — theoretical framework (Swink's 6 metrics, perception thresholds, ADSR theory, principles audit). Use that skill for why / how much; this skill for how.
• game-ux-design — feedback must not obscure critical HUD info (shake budget vs readability)
• engine animation skills (auto-activated via registry) — animation and curve implementation
• tweening library skill (auto-activated via registry) — zero-alloc tweening for juice effects
• engine rendering skills (auto-activated via registry) — GPU-side effects
• engine VFX skills (auto-activated via registry) — particle VFX

Reference Files

File	Coverage
references/hit-feedback.md	Hit stop frames, hit flash, knockback, damage numbers, screen shake, particle bursts
references/screen-effects.md	Shake formula, camera punch, chromatic aberration, time slow, vignette, flash effects
references/animation-curves.md	Ease types, UI animation timing, squash/stretch, anticipation, follow-through, spring physics
references/input-responsiveness.md	Latency budget, input buffering, coyote time, cancel windows, dead zone, priority system