Play as a Martian:
Press Right, Left, Right, Up, Down, Left, Right, Up, Up at the main menu.

Mars tracks:
While pausing the game press Left, Left, Right, Right, Left, Left, Right, Right, Down, Left, Right.

Wide-angle mode:
While pausing the game press Left, Left, Left, Right, Right, Right, Up, Up, Up, Down, Down, Down, Left, Left, Left, Right, Right, Right.