[Edit]

Love the interface stats, although unbalanced at the moment, as I can be beaten as a King by a Rook in just 2 hits  

I have a gameplay suggestion -

Instead of sliding around trying to bash into one another, how about a point-and-click type control system:

 Click a target position
 Hold the mouse to charge your power
 Release the mouse to go flying in that direction

Different pieces could be faster at charging, or have higher damage.

Edit

Seems there are no draws!

Braindump

• I can get past level 3 without needing a bronze star
• Version string on the pause menu differs from main menu
• Level 10 on Challenge 6 relies too much on chance; the critters overlap too much