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topdown-physics experimental

Basic, grid-based, 2D top-down player physics for continuous ndarrays.

You can find a demo here, the code for which is here.

The implementation could be improved a lot - patches welcome :)


Written to be used with browserify.

npm install topdown-physics


physics = require('topdown-physics)(player, field[, options])

player is an axis-aligned bounding box - use aabb-2d for this. field is a continuous ndarray to check collisions against. You can also pass the following options:

  • friction: The amount of friction to apply - the higher the value, the more quickly the player will slow down.
  • physical: A function that should the value of a cell and returns whether or not it is solid, i.e. the player cannot move through it. Alternatively, you can just pass in a constant value. Defaults to 0.
  • interval: The granularity of collision checks - generally, this is best set to the reciprocal of the width in pixels of each cell when rendered. So if each block is 32x32, you should set this to 1 / 32.


Steps forward the simulation by one tick - this should be called each frame.


An array you're free to modify directly. The first value is the horizontal speed (in cells per tick), and the second is the vertical speed.

physics.on('collision', callback)

Emitted when a collision is made during a tick.