bug: FPS cannot be different than 32, moves become imprecise

[itsjavi]

Right now, for making the grid-tile-snapping movement work with tiles of 32 pixels (to always end up inside a full tile) the FPS needs to be also 32.

Something different than that will cause the player to move and overlap outside the tile it is supposed to fill.

To fix this we may need to play more with fps, pixels per frame, tile size and velocity and find a formula. Ideally the game should run at 60fps with grid-snapping.