Added two new retro games:

 * One based on Tetris, particularly inspired by the GameBoy version from 1989. Still has some mechanics missing (e.g. hold to move faster).
 * Another based on the famous Snake from the Nokia 6110 (there are other, earlier games such as Blockade, but this seemed like a good place to start).

Reduce eye straining due to visual effects.

Please feel free to provide feedback so we can make this as fun as can be.

Support further development via Liberapay or GitHub Sponsors.
