I've implemented the final two power-ups; score multiplier and guard. The purpose of the score multiplier is pretty straight forward. When collecting this powerup the multiplier counter goes up by one. However you only get one rebound of the ball before it starts going down again; every subsequent hit lowers the multiplier by one. The exception is if you have multiball; the counter stays where it is until you only have one ball left (or if you lose all the balls, in which case it resets). I'll need to playtest to see if this dynamic works, but it's good to start with.
The guard powerup activates a glowing forcefield at the bottom the screen, so if you miss a ball it is deflected. Each guard powerup gives you one rebound.
I still need to balance all the powerups and the scoring system, but at the moment I'm trying to polish off the graphics to something properly presentable. This is trickier than it seems, especially because I'm not that superb a graphic artist. It's challenging to come up with a set of sprites that look good when put together, as well as both in fullscreen and in windowed mode.
The sprite that has given me the most trouble is the steel brick, which just doesn't look right the way I keep designing it. I've tried several designs (some of which are in the screenshot above), but none of them seem right; they're either too cluttered or don't stand out enough.
I'm currently going to leave it as it is and work on other details, but I'd like to get this brick in better shape before I release a playable demo.
I found a "solution" to the whole steel brick problem - just turn the brick into something else. It's now rock:
With a few more backgrounds, a bit more code and a handful of levels this might approach "releasable demo" status. Then with a few new paris of eyes and hands playtesting this baby I think it might polish up to a nice little brick game.