Painkiller is based along similar lines but retains Doom's darker demonic palette whereas Serious Sam is very light-hearted and colorful. A number of people hav

Painkiller is based along similar lines but retains Doom's darker demonic palette whereas Serious Sam is very light-hearted and colorful. A number of people have mentioned that it is essentially what Doom 3 would have been if ID hadn't changed the series' genre to horror rather than staying an action shooter.