Level 1 - drop into the leftmost hole and land on the island.
Level 2 - Wear the penguin skin and get hit by a snowflak.
Level 3 - Right-click into the level and fire the rainbow gun.
Level 4 - Shoot and destroy the rainbow spikey (you will see it at the bottom near the end moving right to left).
Level 5 - Immediately exit off the left side.
Level 6 - Look for a slightly darker asteroid near the center and destroy it with the rainbow gun.
Level 7 - Right-click into the level and jump off the topmost screen.
Level 8 - Shoot the boss (pounding spike thing) with the rainbow gun (once is enough).

Perfect run, walkthrough: