Ah, yeh yeh, got it working. Just had to install .Net Framework 4.5.1
Had a little play around and it seems quite fun, like a mix of Quake/Unreal/Painkiller. Weapons/Monsters are quite clever ish, pickups etc are all unique to the monster/weapon you're using when you aquire them. The Weapons/Monsters are comparable to Quake weapons but do have alt fires that mix the gameplay up a bit.