Basicly kill Kraid in 10, 24, and 30, beat Ridley in 7, (It can be done!) 20, and 28, and 30. And of course kill Ice Ridley in 22, 26, 28, and 30. Some rules i thought of:

• You can kill all three bosses in the same level
• You could also add master the levels they appear in
• You only need to kill the bosses, not complete the level. You could quit after beating Ridley.

Could be a fun challenge.

Why not, this could be intresting