Games like Project Ara - Crucible
Games like Project Ara - Crucible include Vampire Survivors, The Binding of Isaac, Megabonk, Enter the Gungeon, and UBERMOSH. We matched them by the tags players give Project Ara - Crucible on Steam (Action, Indie, Bullet Hell, and Procedural Generation): closest matches first, and among equally close ones the better-known games.

Vampire Survivors
Shared: Bullet Hell · Indie · Action

The Binding of Isaac
Shared: Indie · Action · Procedural Generation

Megabonk
Shared: Indie · Bullet Hell · Action

Enter the Gungeon
Shared: Bullet Hell · Indie · Action

UBERMOSH
Shared: Action · Indie · Bullet Hell

Windowkill
Shared: Action · Indie · Bullet Hell

LUFTRAUSERS
Shared: Indie · Bullet Hell · Action

Nuclear Throne
Shared: Indie · Action · Bullet Hell

Death Must Die
Shared: Bullet Hell · Action · Indie

Superflight
Shared: Indie · Procedural Generation · Action

Atomicrops
Shared: Action · Bullet Hell · Indie

Skul: The Hero Slayer
Shared: Action · Indie

ScourgeBringer
Shared: Action · Indie · Bullet Hell

Exit the Gungeon
Shared: Indie · Action · Bullet Hell

Star of Providence
Shared: Bullet Hell · Indie · Action

Touhou Fuujinroku ~ Mountain of Faith.
Shared: Action · Indie · Bullet Hell

Just Shapes & Beats
Shared: Bullet Hell · Indie · Action

Hotline Miami
Shared: Action · Indie

UBERMOSH:WRAITH
Shared: Action · Indie · Bullet Hell

Hades
Shared: Indie · Action

TouHou Makuka Sai ~ Fantastic Danmaku Festival
Shared: Indie · Action · Bullet Hell

UBERMOSH:BLACK
Shared: Action · Indie · Bullet Hell

Bleed 2
Shared: Action · Indie · Bullet Hell

Touhou Blooming Chaos 2
Shared: Action · Indie · Bullet Hell