Game feel with AI: 12 juice techniques to ask for

Game feel is how a game answers your input: how a jump lifts off and lands, how a hit connects, how the screen reacts. A coding agent builds what the prompt describes, and most prompts describe mechanics. Ask for a jump and you get a jump that works.

The small timings that make it feel good, like a three-frame pause on a hit or a sound pitched slightly differently each time, arrive only when someone names them. This page names twelve, each with a value to start from.

Where these techniques come from

Two talks gave most of them their names. At GDC Europe 2012, Martin Jonasson and Petri Purho gave “Juice It or Lose It”. Live on stage, they took a plain block-breaker and cranked it up one effect at a time (GDC Vault, video).

A year later, at INDIGO 2013, Jan Willem Nijman of Vlambeer did the same to a shooter in “The Art of Screenshake” (video). Watch either one before you prompt, and borrow freely.

The 12 techniques

The values below are starting points to tune by feel.

Movement

1. Coyote time. A jump still works for a moment after the player leaves a ledge. Maddy Thorson lists it first among the forgiveness tricks in Celeste (Celeste & Forgiveness). Start around 0.1 seconds.

2. Jump buffering. A jump pressed just before landing fires on the frame the player lands, instead of being lost (Celeste & Forgiveness). Start around 0.1 seconds.

3. A softer jump peak. Celeste halves gravity at the top of a jump while the button is held, which gives the player time to aim the landing (Celeste & Forgiveness). Pair it with variable jump height: release early, fall early.

Impact

4. Hit stop. Freeze the action for a few frames when a big hit lands. Masahiro Sakurai, who directs Super Smash Bros., made it the subject of his first Design Specifics video (Stop for Big Moments). Start with 3 to 6 frames for a normal hit and more for a finishing blow.

5. Screen shake that decays. A short, sharp shake on impacts, which fades within a fraction of a second. Scale it to the event: a footstep gets none, an explosion gets the most. Shake the camera, never the UI.

6. Knockback and recoil. The target gets pushed back, and so does the shooter. Nijman’s talk adds both to a shooter and shows how much weight they give (video).

7. Particles and flashes. Dust when you land, sparks when you hit, a one-frame white flash on the enemy that took damage. Particles should obey the world, with a little gravity, a little drag and a short life.

Motion and camera

8. Easing. Linear tweens look mechanical. Menus slide in and slow down at the end (ease-out), and pickups pop past their size and settle back. Ask for easing on every tween.

9. Squash and stretch. Stretch the character up on takeoff and squash it on landing, keeping its area roughly the same. Ten to twenty percent is plenty for a character; a jelly can take more.

10. A camera that leads. The camera looks a little ahead of where the player is moving and follows smoothly instead of locking on. A small dead zone stops it from twitching when the player twitches.

Sound and UI

11. A sound for every action. Jump, land, hit, pick up, click: each gets a short sound, pitched slightly differently each time, around 5 to 10 percent, so repeats don’t grate. AI sound effects and music for games covers making them and playing them in a browser.

12. Feedback in the numbers. Scores count up instead of jumping, damage numbers pop out of the enemy, and the combo counter grows and shakes a little with each hit.

Spot them in the catalog

Several listed games wear their juice openly. Arkanoid Neon gives hits weight with particle bursts, shockwaves, screen shake and ball trails, and its README says Claude Opus 5.5 made the whole game through Claude Code. JellyBlob renders each player as squashy, see-through gelatin, and Floppy Brawler builds its fights around loose-limbed ragdoll physics.

How to prompt for it

One technique per prompt, with a number to start from, and every number in one place:

Add hit stop: when the player’s attack connects, freeze the game for 4 frames, and 8 frames on the hit that defeats an enemy. Put both values in src/config/feel.js. Don’t freeze the UI or the music.

Three habits keep the tuning fast:

• Keep all feel values in one file. Coyote time, shake strength, hit stop frames, easing curves. Tuning becomes a one-line change you can ask for, or make yourself.
• Add a live tuning panel. Ask for a debug panel, hidden behind a key, with a slider per value. Ten minutes of dragging sliders beats ten rounds of “make it a bit snappier”.
• Add a master switch. One flag turns every effect off. Flipping it replays Jonasson and Purho’s on-stage demo in reverse, one effect at a time, and shows whether each effect earns its place.

Don’t drown the game in effects

Not every developer buys the juice philosophy. At GDC Europe 2014, Folmer Kelly argued that the focus on eye candy costs games some immersion (Game Developer). A useful test is to turn an effect off and play for a minute. If you miss it, keep it. If you don’t notice, cut it.

Make it comfortable for everyone

Screen shake and flashes make some players sick, or worse. Browsers report a player’s reduced-motion setting through the prefers-reduced-motion media query (MDN), and one line reads it:

const reduceMotion = matchMedia('(prefers-reduced-motion: reduce)');
const shakeScale = () => (reduceMotion.matches ? 0 : settings.shake);

Offer a shake slider in the settings either way. Keep flashes to three per second or fewer, since WCAG’s flash guideline exists because flashing content can trigger seizures (W3C).

Next: sound and playtesting

• AI sound effects and music for games: the other half of game feel.
• Playtesting games with AI: let the agent check that the effects didn’t break the game.
• Make a game with AI: 10 prompts to copy and adapt: prompts for every step before polish.
• Play the top rated games and look for the techniques above. Once you see hit stop, you can’t unsee it.