V2.0:
Added new UDG for the satellite, and radiation counter.

V3.0:
Number of satellites increases to seven. Radiation now increases in
both directions.

V4.0:
Satellites must now be collected in order shown by blue numbers above
them, which changes each time. "Missions expired" changed to the same
style as other deaths. "New game" leaves out the instructions. Only 8
missions available instead of 10.