Steam now offers the new free "Level Up" content pack for Killing Floor, which adds three new maps, seven weapons, and 20+ Steam Achievements to Tripwire Interactive's co-op zombie shooter. The free weekend for the game is also underway, so the game and its new content can be sampled by anyone with a Steam account. In addition to the 100% discount that the free weekend represents, the game is now on sale for a 25% discount if you are inspired to make a purchase.