View credits:
Press Left, Right, Up, Down, Left, Right, Up, Down, Left,
Right, Up, Down, Left, Right, Up, Down, Left, Right, Up,
Down at the mission briefing screen.
Secret missions:
1A - Finish mission 1 in under five minutes, two seconds
with more than 40 percent accuracy.
4A - Finish mission 4 in under six minutes, 44 seconds
with more than 40 percent accuracy.
5A - Destroy half of the energy plough and pull the other
half in with the tractor beam.
5B - Look for an info unit between the two asteroids
somewhere near the broken shuttle and pull it in with the
tractor beam.