Bonus points: Locate the rooms in the ships that contain green faces
on the floor. Collect 500 points for killing them, then wait until
they re-appear. Kill them again for another 500 points.
Temporary invincibility: Wait until 272, 267, 232, 222, 171, 161, 131, or 121
is displayed on the counter, then collect the boxes with the question
marks from the ships.
