Proper player speed

For now, the player movement model is the following:
- we have three levels of engine power for both X and Y axis
- each power grants 1 px per tick movement
- both X and Y are independent, so you can move by 3x+3y max per tick

While this resembles the original, I'm not sure how accurate it is. Please measure the original game speed (I use OBS + MPC-HC to track concrete frames) and make sure our rules are the same as in the original.