World 3 - Level 4
Friend or Foe
Collect hidden Bonus Coins at the blue circles. Then push the prisms so that each yellow "X" is occupied. Move the final prism along the red path into the corner, then align the reflectors as shown, and release the cannon (you only get one shot).
The final coin can be released by using the remaining prism and pushing it along the green arrow. This will deflect the Rainbow Spirit. The final part is a little tricky - you have a 50/50 chance that the Rainbow Spirit will collect the coin on the first go, otherwise it will start bouncing around the level. Avoid it (and others) until the coin is collected and exit.