Save for Wrecking Ball, UFO, and Antimatter! (Most useful things you can buy in the Shop!)
Try keeping your aim in the middle and pay attention to what color the hedgehogs are and what keys you're pressing! ^.^
VERY FUN! Although level 24 is impossible for me. xD Congratulations for all who succeeded in that level! :D
Want more jewels? Just simply walk out of a map and walk back inside. All your previous jewels will be there!