Games like Quantum Contours
Games like Quantum Contours include Deep Rock Galactic: Survivor, Brotato, Vampire Survivors, Enter the Gungeon, and BALL x PIT. We matched them by the tags players give Quantum Contours on Steam (Bullet Hell, Top-Down Shooter, Arena Shooter, Boss Rush, and Action Roguelike): closest matches first, and among equally close ones the better-known games.

Deep Rock Galactic: Survivor
Shared: Bullet Hell · Action Roguelike · Top-Down Shooter

Brotato
Shared: Bullet Hell · Action Roguelike · Arena Shooter

Vampire Survivors
Shared: Bullet Hell · Action Roguelike · 2D

Enter the Gungeon
Shared: Bullet Hell · Action Roguelike · Indie

BALL x PIT
Shared: Bullet Hell · Top-Down Shooter · Action Roguelike

Nova Drift
Shared: Bullet Hell · Arena Shooter · Action Roguelike

20 Minutes Till Dawn
Shared: Bullet Hell · Action Roguelike · Top-Down Shooter

Nuclear Throne
Shared: Action Roguelike · Bullet Hell · Top-Down Shooter

Glyphica: Typing Survival
Shared: Bullet Hell · Arena Shooter · Top-Down Shooter

Tiny Rogues
Shared: Bullet Hell · Top-Down Shooter · Action Roguelike

The Binding of Isaac
Shared: Action Roguelike · Dark · Indie

SNKRX
Shared: Arena Shooter · Top-Down Shooter · Action Roguelike

Arms of God
Shared: Top-Down Shooter · Bullet Hell · Action Roguelike

Time Wasters
Shared: Bullet Hell · Action Roguelike · Arena Shooter

FatalZone
Shared: Bullet Hell · Action Roguelike · Top-Down Shooter

Pathogenic
Shared: Bullet Hell · Top-Down Shooter · Action Roguelike

Chippy
Shared: Bullet Hell · Arena Shooter · Top-Down Shooter

The Last Stand: Aftermath
Shared: Top-Down Shooter · Action Roguelike · Shooter

Relic Hunters Zero: Remix
Shared: Top-Down Shooter · Action Roguelike · Bullet Hell

Halls of Torment
Shared: Bullet Hell · Action Roguelike · Action

Star of Providence
Shared: Bullet Hell · Action Roguelike · 2D

Rocket Rats
Shared: Bullet Hell · Action Roguelike · 2D

SYNTHETIK: Legion Rising
Shared: Top-Down Shooter · Action Roguelike · Indie

Noobs Are Coming
Shared: Bullet Hell · Arena Shooter · Action Roguelike