arrow keys to move, E is to shoot. In the starter room jump across the platforms to get to the other side. Then rapidly shoot Venom and his hosts until he dies. Beware! the floor falls away and you might want to grab the golden egg as you make your way past to the next level. This level requires skill and speed. You must head down the tunnel to escape Carnage who starts digging down immediately. I wouldn't let him go first as he may dig through some platforms at the bottom you might need! Then you can sit and stare at the flashing 'Thanks' sighn at the end.
Unfortunately, there's this really annoying glitch when becoming steve. When the egg cracks 2 or more steves appear instead of one. This may not seem a problem but remember you have to get all the Steve's over the lava to the other side. If you cannot do this after many tries just open editor and play the next level (the great cave).