---
title: "Platform hazards"
package: "@phaser-ae/platform-hazards"
tier: Pro
version: 3.0.0-1
released: 2026-10-19
updated: 2026-10-20
description: "Enemy projectiles, invincible chasers and extra enemy behaviours for single-screen platform games, from lobbed bombs and boomerang bottles to wall-to-wall flyers, sentries and bosses."
url: https://phaser.io/packs/platform-hazards
site: Phaser - https://phaser.io
---

# Platform hazards

Enemy fire, invincible chasers and extra enemy behaviours for single-screen platform games. Projectiles and chasers
are plain data specs, and the behaviours slot into `platform-enemies` as custom moves.

## What it does

`EnemyShots` moves enemy projectiles over a platform map. A shot spec names the kind, its speed and size, and how it
is aimed: straight ahead, straight down, at the target or lobbed in an arc with its own lift and gravity. It can live
for a time or a distance, rebound off walls instead of breaking, fly back to its thrower after its range, ignore the
map like a laser through floors, or leave a burning patch where it lands. The kind is a free name, so your renderer
and rules decide what a rock, a bottle or a bomb looks like and does.

`Chasers` handles the enemies the player cannot kill and must keep away from: one that lines up with the target on one
axis and then the other, accelerating to a top speed and tiring after a while; one that flies straight at the target;
and one that drifts and rebounds off the screen's edges, which a player's shot can stun and throw somewhere else.

`hazardBehaviours` registers seven enemy behaviours with `platform-enemies`. They return walker intents like the
built-in moves and call your `shoot` and `summon` hooks for projectiles and minions, so scoring and objectives stay in
your rules.

## Features

- **Aimed shots** — facing, down, at the target or in an arc, with lift, gravity, lifetime and range.
- **Projectile variations** — bouncing, boomerang returns, passing through the map, and burning patches on impact.
- **Invincible chasers** — axis-alternating, homing and wandering movers with acceleration, top speed, tiring, size
  and a choice of whether touch is deadly.
- **A hunter behaviour** — walks, turns at walls, decides at edges, jumps up through platforms toward a higher
  target, takes running jumps, shoots, dashes and drifts toward the target.
- **Six more behaviours** — `wall-flyer`, `invader`, `spring`, `sentry`, `perch` and `boss`, the boss holding a side,
  hopping, summoning minions and firing, or ricocheting when it flies.
- **Hit tests** — which shots or chasers overlap a box, for your rules to act on, and a call to teleport a chaser.
- **Deterministic** — pure movement over the map, seeded randomness for chasers, and snapshot and restore.

## Good for

- **Bubble-trapping platformers** in the style of Bubble Bobble, with rock-throwers, wall-to-wall flyers and an
  invincible chaser that lines up axis by axis.
- **Snowball platformers** in the style of Snow Bros, with a pumpkin head a shot throws aside and homing ghosts.
- **Single-screen platform rounds with a boss** that guards a side and summons minions.
- **Any platform game whose enemies shoot**, from straight rocks to lobbed bombs that leave fire behind.

## Make it yours

Every number is data. A shot spec sets speed, size, aim, lift, gravity, life, range and the bounce, return,
pass-through and burn flags. A chaser spec sets its movement, speed, acceleration, top speed, tiring time, size,
deadliness and what a shot does to it. The behaviours read their numbers from each kind's parameters: how often and
how far a hunter shoots, whether it dashes, how a boss chooses its side and how often it summons. You can also raise
the cap on projectiles in flight.

Two quite different uses: a bubble game whose monsters walk, jump up through floors and throw rocks, with a chaser
that lines up axis by axis and tires after thirty seconds; or a snowball game with a wandering pumpkin head that a shot
throws elsewhere, homing ghosts and a boss that holds the right side and summons minions.

## A quick look

Shots, a chaser and the behaviours registered with the enemy director:

```ts
const shots = new PH.EnemyShots(map);
shots.fire(enemyId, { kind: 'rock', speed: 100, w: 4, h: 4 }, x, y, facing);
const chasers = new PH.Chasers(map, game.kernel.rng.fork('chasers'));
chasers.add({ kind: 'baron', move: 'axis', speed: 24, accel: 9, max: 96, tire: 30 }, 128, 16);
const enemies = createEnemies({ world, kinds, behaviours: PH.hazardBehaviours({ shoot: (id, shot, at) => fire(id, shot, at), summon: (id, kind) => spawnNear(id, kind) }) });
```

## Works with

- `platform-map` — required: the map shots fly over and collide with.
- `platform-enemies` — the director the behaviours plug into.
- `enemy-capture` — builds its bubble and snowball monsters from these behaviours.

## Good to know

- Projectiles are boxes moving in lines or arcs, tested against map cells, not against moving platforms.
- Chasers fly over the map and do not find paths.
- At most 128 projectiles are in flight by default; pass a larger limit when you create `EnemyShots`.
- The pack decides nothing about hits or deaths: your rules ask which shots and chasers overlap the player's box
  and decide what that means.

---

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