Zombie Processes - they shamble in from wave 3, and killing one isn't enough. It goes down and lies there defunct: shoot the body or dash through it before it gets back up (kill -9), or it rises as a ghost that's faster and floats straight through props

Cursed wave 13 - every 13th wave the build server loses power. The screen goes dark and your aim is the only light, muzzle flashes, explosions, portals and jack-o'-lanterns light things up for a moment, and all you can see of the horde is their eyes. Something in a bedsheet is coming

SCOPE CREEP - a new boss made of feature requests. It starts as an MVP, then it's an MVP + multiplayer, then an MVP + multiplayer + open-world MMO, and it keeps growing for as long as you let it live

Unlabeled commits - a new card in the commit picker with no message and no diff. Trick or treat: a free rare or epic commit, or a regression ships with the next wave

Haunted build - a new patch note: some of the dead come back, some of them in bedsheets

Achievements - 3 new ones: kill -9, Power Restored and Scope Cut

Costumes - some Placeholders come as jack-o'-lanterns or bedsheet ghosts, and T-Posers wear witch hats

gm_graveyard - a new map at night, with a tombstone for everything we shipped: RIP FLASH, RIP CS:S, RIP MY WEEKEND

Pumpkins - jack-o'-lanterns on every map, and SCOPE CREEP is always the first boss

Main menu - dressed up too: a moonlit arena, fog, bats, a spider, cobwebs, a jack-o'-lantern and slime on the logo, and a music box playing somewhere

After Halloween - Zombie Processes, the cursed wave 13, SCOPE CREEP and unlabeled commits stay. Only the costumes and the graveyard go back in the box