The Abandoned Casino level.

The best I've done so far is six mobs that leaked through. It's pretty difficult because the mobs spawn so close and there's no way to block them off effectively. It seems to me that you need to use a lot of traps that push or pull to thin them out. Once I get to round six the sheer number of mobs that come out just overwhelm my traps and some sneak past.

I put a bunch of spring traps down in front of the gate to launch them south (so they have to come around the corner) and some black hole & spring traps north to launch them onto the long minecart track. I then space out some harpoons and push traps to try and thin them out as they walk back around. Placing a single barricade next to the dungeon core on the left side prevents the mobs from walking that way so you don't need to worry about trapping that area at all. Finally, a few damage-dealing traps along with the Lich trap sprinkled around to kill the weak ones before they get back to the launch-a-thon.

Has anyone been able beat this one perfectly yet? The thought of having to do this one with six runes makes me sweat.

Also, any clues as to what the slot machines actually do? I saw "XP" pop up a few times so I assume that they give a random amount of XP if you beat the level.