fyi, you need a bounds check on ball location each iteration.. just got a memory access error when a fast ball i spawned snuck out of a corner (my "hole" was only about 30 wide by .. maybe 40 tall (oddly shaped of course), but a freshly spawned fastest-ball just snuck out, and effectively when it hit the went out of the grid, the browser threw an error.
nice concept, but not going to play again until there's a save game.