And Here's the Thing About Powerups:

I was thinking they'd be one-shots that you could suck up and activate (as bonuses). Having them as "collectibles" requires that there be an Inventory, which requires that there be a Heads-Up Display (which is what we're trying to avoid with the fuel-tank icon system).

Also, being able to collect multiple parts and powerups is more confusing (muddying the simple Bust-a-Move-ish mechanic).

I do think that holding a button down to charge the cannon is a good idea. I also think that repositioning the cannon with the cursor might work- instead of 'cannon left' and 'cannon right' controls, I mean. I don't think the mouse should be locked to any one part at any time.