Hit points, bumping, more sounds

I added a sound for asteroids breaking up, and similar to the joining event the volume it plays at varies by size. However, it seems like it's not possible for sounds to go over 100% volume? So currently breaking up an asteroid the mass of the ship sounds no different than breaking up one with 100x the mass of the ship. Not that being 100x the volume would be a good thing, but I wish it was louder. Might have to adjust things so it's a louder sound to begin with, and then asteroids the size of the ship are at 25% or 50% of that volume?

Implemented hit points system for asteroids. Ship bullet's power scales with mass, as do asteroid's hit points. So something with 10x the mass of the ship currently takes 10 bullet hits to destroy. This might be a bit much--it's feasible, and INTERESTING, to have the occasional giant asteroid, but needing to shoot it 1000 times or avoid it for a long time might be a bit much. I also wonder about the best way to display how much HP an asteroid has left? Temporarily I've got it sitting along the mass text at the top left, but something more immediately visual might be good. Like, if it's standardized that all asteroid shapes have a white border, implement some effect where the closer it gets to 0, the white shifts more to red?

I've adjusted bullet strength to 10x ship mass. So something with 300x ship mass now takes 30 hits.

Added in some interaction with larger asteroids. Whereas those 1/4 the mass of the ship are joined, now those greater than that but less than 4x ship mass will bump away. It's not exactly physics accurate or consistent, but it affects an asteroid's motion in vaguely the direction the ship is headed (slightly random) and adds to its speed by a fraction of the ship's speed (currently set to 1/3), with a speed cap the same as the ship's. At first it was making these asteroids fling away because the direction/speed alteration was happening repeatedly, but I added in a little timer with current_time so once it's had a "bounce" event it won't again for at least 2 seconds. Also added in a bounce noise, which again has its volume modified by asteroid size. Probably a good idea to have the ship's direction/speed affected too, but I haven't put that in yet.