A method for testing collision / intersection between two circles on a 2D surface is presented below in Javascript. Code in made as simple as possible to support adaptation to other languages.

```
function circlesIntersect(c1, c2)
{
return (c1.r + c2.r) >= (Math.abs(Math.sqrt(
((c1.x-c2.x) * (c1.x-c2.x)) +
((c1.y-c2.y) * (c1.y-c2.y)))));
}
```