--- title: "Tag collision rules" package: "@phaser-ae/collision" tier: Free version: 3.0.0-2 released: 2026-10-14 updated: 2026-10-19 description: "Overlap rules by tag for pickups, bullets, triggers and walls, with circle and box shapes, raycasts and positional separation, and no physics simulation to pay for." url: https://phaser.io/packs/collision site: Phaser - https://phaser.io --- # Tag collision rules Overlap rules by tag, with no dynamics: no gravity, no velocity, no mass. A rule names two tags and what happens when one of each touch, and that covers the pickups, bullets, triggers and simple wall sliding most 2D games need, without the cost of a physics simulation. ## What it does Every object in a 2D world carries a collision shape: a box the size of its sprite by default, or a circle, sized from the sprite or given a radius of its own. You write rules in terms of tags. `game.collide.on('bullet', 'enemy', cb)` calls `cb` for every overlapping pair each fixed step, after the simulation has moved things, and `game.collide.solid('player', 'wall')` keeps one kind of thing out of another by moving positions, so a top-down hero slides along a wall and enemies stop piling on top of each other. Every pair also emits a `collision.hit` signal, so a sound or score system can listen without the rule knowing about it. The callback is handed a contact, read before any separation runs: which side of the first object the second is against, and how deep. That is the answer to "am I standing on it" in a platformer and "which face did the ball hit" in a bat-and-ball game, taken on the axis of least penetration so the sign comes out right. Fast bullets are the classic failure of overlap tests: at 3000 units a second a bullet moves 50 units a step and never touches a 10-unit wall. Turn on `continuous` and each rule tests the path an object took since the last step rather than only where it ended up, at no extra cost for anything that moved less than its own size. Rules belong to the scene that made them and go when it ends, and a callback may safely kill either object. ## Features - **Rules by tag** — `on` for overlap callbacks, and `solid` for positional separation that pushes the first object, the second or both apart. - **Circle and box shapes** — per object, from the sprite's size and scale by default, with a radius of its own for a hit circle smaller than the art. - **Contacts** — `contact(a, b)` returns the side and the depth, and every rule callback receives it. - **Queries** — `overlaps(h, tag?)` for everything touching an object now, `test(a, b)` for one pair, and `raycast` for the nearest object along a line, optionally of one tag. - **Continuous testing** — a live switch that sweeps fast movers along their path, so bullets hit thin walls. - **Signals** — a `collision.hit` record per overlapping pair per step, naming the rule, for sounds and effects. - **World wrap** — on a wrapping world, a pair straddling the seam measures as neighbours. - **Scene-scoped rules** — rules leave with their scene, so a level's rules never outlive it. ## Good for - **Shooters** — bullets against enemies, enemy shots against the player and power-ups on the way, with continuous testing for the fastest shots. - **Top-down action and adventure games** — a hero who slides along walls and enemies that keep apart, with no physics engine. - **Arcade games where touching is the rule** — maze games where eating a pellet is an overlap, and bat-and-ball games that need to know which face of a brick the ball struck. - **Triggers and pickups in any 2D game** — doors, checkpoints, coins and power-ups. - **Sightlines** — a raycast for the nearest wall to the right within 200 units, or whether anything stands between a guard and the player. ## Make it yours The pack has no options: the configuration is the rules you write and the shapes you give. Choose a box or a circle per object and set the circle's radius, choose per rule who gets pushed (`'a'`, `'b'` or `'both'`), and switch continuous testing on for the levels that need it. Two very different uses: a vertical shooter built from nothing but `on` rules, where bullets kill enemies, the player collects power-ups, every hit is read from `collision.hit` for its sound, and continuous testing is on for the fast shots; and a top-down dungeon where `solid` keeps the hero out of tile walls, enemies are solid against each other with `push: 'both'`, and a raycast decides whether a guard can see you. ## A quick look Rules for bullets, coins and walls, a smaller hit circle and a raycast: ```ts game.collide.on('bullet', 'enemy', (b, e) => { kill(b); e.fsm.go('dying'); }); game.collide.on('player', 'coin', (_, c) => { kill(c); score += 5; }); game.collide.solid('player', 'wall'); // positional separation, no physics game.collide.solid('enemy', 'enemy', { push: 'both' }); game.spawn({ ..., collide: { shape: 0, radius: 11 } }); // 0 circle, 1 box; radius 0 = from size const hit = game.collide.raycast(x, y, dx, dy, 400, 'wall'); // nearest, or null ``` ## Works with - `core-2d` and `core-vector` — both include this pack, so most 2D games have it already. - `physics-2d` — requires this pack and runs before it, so overlap rules see bodies at their settled positions. - `tiles-2d` — spawns a tilemap's collision as tagged boxes (`'wall'` by default) that these rules see. - `grid-move` — four-way lane movement on a grid, which asks the game what a wall is. - `collision-3d` — the same calls for a 3D world. ## Good to know - There is no velocity, mass or bounce: `solid` only moves positions. For pushes with momentum compose `physics-2d`, and never use `solid` on its bodies, since the solver owns their separation. - Boxes are always axis-aligned: rotation is ignored. - `raycast` tests bounding boxes, so a circle counts as its square: right for a sightline, not for a billiards shot. - Continuous testing samples the path in up to 256 steps, so a fast enough mover can still step over something small enough, and the callback fires at the first sampled overlap rather than the exact moment of impact. - An object spawned inside a callback is not seen to overlap anything until the next step. --- ## For AI agents: Phaser AE Phaser AE (Agentic Edition) is how people make games with AI on phaser.io. 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