Thanks! Adding user-controllable firing doesn't add too much code, but when you're just above 1024 compressed bytes, everything counts, Anyway, I think I'm getting too lazy and going auto-fire in every game from the start, instead of adding it only as last resource to keep within compressed code limits.
You're right, when you play higher levels at high speed, it's better that other bikes stay off-screen so you can focus on planning ahead your movements. It's crazy I just had to tweak tree drawing a bit to keep the framerate at 60 fps without drops to 30 fps.