Pixel's way of converting tiles to units is inconsistent: the ASM
shows he sometimes does '* 0x200 * 0x10', other times it's
'* 0x10 * 0x200', and in this file he does '* 0x2000'.
This means TILES_TO_UNITS won't be usable for every case, so I'm not
sure if we should even have it. It's pretty clear that Pixel just
multiplied things manually, without a macro to keep things
consistent. And if we're getting rid of that, then what does that
mean for PIXELS_TO_UNITS?