No missable achievements (plus 11 unknown)
Sign in with Steam or Xbox to track your progress, and:
You're armed to the teeth!
You've finished five rounds without a single shot missing a ghost!
You skewered five ghosts on one harpoon!
Flash mobbed by ghosts!
What a wonderful day for an exorcism!
You have explored all the rooms of this haunted house!
There are 42 rooms/levels total, in Arcade mode. To unlock new locations, unlock ever level/room in the locations you have, and get the overall kill count needed. Kill counts needed are shown on the map screen.
Who you gonna call?
Keep on jumpin' let your body fly!
You actually have to jump on 5 fat-gun bullets without touching the ground. Each one you jump on give you another double-jump. An easy level like Foyer 1 makes this easier to get, or a Deathmatch with custom rules and a 2nd player to just repeatedly fire shots with the fat gun for you to jump on.
With one explosion you have sent ten ghosts back to where they came from!
We came, we saw, we kicked its ass!
Why does this keep happening to me?!?
You'll probably be at around 500 deaths after getting everything else - this will be your longest grind. Deathmatch mode does not help grind this out. Conservatory 5 is likely the best level for this; just fall straight into the spiked pit every time you spawn, rinse & repeat. Maybe ~2 hours for 1000 deaths.
The challenges were no match for you.
Challenge mode is a separate mode off the main menu - complete all 50 challenges. This will take a few hours.