Oh no, the blue zombies took your cheese! Use A, D, and Space to head east to the headquarters building where they are keeping your cheese at the very top. There are buildings in the way; use left click to pick up blocks and left click again to place them. When you are holding a block you can hold right click to charge up throwing the block. Higher mass blocks do more damage, but are harder to throw. If you're low on health, look for health packs high up in the buildings. Go quickly, before the bomber destroys everything!