Although the x3 Alien Point upgrade offers the least change in AP/gem, it's the most valuable of the three because it offers the most in log(AP)/gem. (Ex: 60 gems can get you a x8 w/ 5 gems to spare, or it can get you 3 x3s = x3^3 = x27)
If you're ascending while hooked and moving left or right, your hook moves with you. Moving the hook into an inward corner gives 2 additional combo increments.
It's fun using unusual block-stacking to do weird things like skipping the first portion of the level that introduces TNT (level 4?) and standing on top of the zombie stack in #8 while it's still in the ceiling.
The fluid dynamic is nice, but large flowing regions in certain cases tend to split and make levels impossible. I can't complete Level 13 due to this. Oh, and placing the color icons off to the side so they don't overlap the level will prevent misclicks.