My bad - my previous comment was not related to that entry - note to self: Don't have multiple tabs open when rating :'D
Fun gameplay, sweet feedback on the shotgun - although some camera shake would really spice it up. The zombies are quite agressive, as someone already mentioned below - but I actually enjoy it since you need to have the Doom gene in you to succeed :) The only thing I'd change is the attack range of the zombies. It sometimes felt unfair to get hit.
Also, I love the aesthetics! Hit a sweet spot for me.
Overall, great entry! Nice job, keep it up ;)