Instructions:
| WASD to move the player/line
| X to start and end a line
| Use your cursor to select things
And not in the instructions:
* click on a computer to enter a level
* walk next to a large black square to see a zoomed out level select screen.
It's easy to miss the instructions because any click or X/space on the 'insert cartridge' screen causes the title screen to close as soon as it loads.