Oasis is the third secret area implemented into the game. The whole level is underwater. Characters, Bandits, and I.D.P.D. forces in this area are inside air bubbles apart from Fish and Robot. Using a Lightning Weapon in this area will damage everything on the screen, including your character. Fire Weapons won't work, the Flare Gun will only do impact damage, and Flame Pellet Weapons won't have the burn effect and will only do impact damage.
The Oasis can spawn on any level of the Desert, meaning it could technically be 1-2, 1-3, or 2-1 in terms of difficulty. Beating this area teleports you straight to 3-3, which means you skip the Sewers and Scrapyard. The game's difficulty does not compensate for this level skip, so while a regular run will be at 7 difficulty by 3-3, a run which uses the Oasis path could be at as little as 3 difficulty.
How to enter the Oasis
Open the Ammo and Weapon Chests and the Radiation Canister on any Desert level without killing too many enemies, which is 2% of enemies on 1-1,1-2 and 10% on 1-3. Opening the chests will spawn Big Bandit. If you kill Big Bandit faster than 10 seconds, the portal to Oasis will open on his corpse. This will kill most of the remaining enemies in the area. If you didn't manage to kill Big Bandit in time the regular level ending portal will teleport you to the Sewers, even if you spawned Big Bandit in 1-1 or 1-2.
- Y.V. as a Gun God doesn't have to breathe but "he has an air bubble so his money doesn't get wet" - Jan Willem Nijman
- The music for Oasis was made by Jukio Kallio in collaboration with Danny Baranowsky, who created the soundtracks for The Binding of Isaac, Super Meat Boy, and Crypt of the Necrodancer.
- The Oasis theme is "Under Water".
- There is an unused boss named "Big Fish". While never implemented, the boss is fully sprited and exists in the game files. When meeting the criteria above for spawning Oasis, Big Fish was supposed to take the place of the boss that spawns, but ultimately was not added to the game.