I think that 'chance time' is broken - if it is supposed to give bricks back I don't see it happening. Maybe not fully implemented in this version? I see that there is apparently another version that puts your barricades behind you so you aren't blocked when shooting, but that changes the game quite a bit.
Anyway, a few more rounds today and I cleared the 20k mark. My secret? Try to shoot them when they come out of the mother ship and hover around that spot still shooting until they stop coming. Then, mop up the rest. The game gets out of control quickly when the screen fills up with baddies and you can't get a bead on any one target, so it's best to get them before they start stealing rather then try to chase down a whole bunch at once.
They also have to bring the bricks to a specific spot, so toward the end of the game when they have to finish the 'D', just wait for them on that side. I went for 2 more unexpected rounds one game with only a few bricks left before THE END was spelled out, just waiting for them under the D. <---insert penis joke here
My pc isn't recognizing my camera sd drive for some reason.. going to reboot and post pic then.