Games like Ocnus Theory
Games like Ocnus Theory include Hollow Knight, Hollow Knight: Silksong, Rain World, Celeste, and Geometry Dash. We matched them by the tags players give Ocnus Theory on Steam (Physics, Difficult, Singleplayer, Platformer, and Exploration): closest matches first, and among equally close ones the better-known games.

Hollow Knight
Shared: Difficult · Platformer · Singleplayer

Hollow Knight: Silksong
Shared: Difficult · Singleplayer · Platformer

Rain World
Shared: Difficult · Exploration · Platformer

Celeste
Shared: Difficult · Precision Platformer · Platformer

Geometry Dash
Shared: Difficult · Singleplayer · Precision Platformer

Cairn
Shared: Difficult · Exploration · Singleplayer

Getting Over It with Bennett Foddy
Shared: Difficult · Physics · Singleplayer

MIO: Memories in Orbit
Shared: Platformer · Exploration · Singleplayer

Peaks of Yore
Shared: Physics · Difficult · Platformer

Totally Accurate Battle Simulator
Shared: Physics · Singleplayer · Simulation

Slime Rancher
Shared: Singleplayer · Exploration · Colorful

The Witness
Shared: Exploration · Singleplayer · Difficult

PEAK
Shared: Physics · Exploration · Adventure

Super Meat Boy
Shared: Difficult · Platformer · Precision Platformer

The Long Dark
Shared: Exploration · Singleplayer · Atmospheric

Ori and the Will of the Wisps
Shared: Platformer · Singleplayer · Exploration

Kerbal Space Program 2
Shared: Physics · Exploration · Difficult

Kerbal Space Program
Shared: Physics · Singleplayer · Simulation

Jump King
Shared: Difficult · Precision Platformer · Platformer

Firewatch
Shared: Singleplayer · Atmospheric · Exploration

LIMBO
Shared: Platformer · Singleplayer · Indie

A Difficult Game About Climbing
Shared: Difficult · Singleplayer · Platformer

Fallout 4
Shared: Singleplayer · Exploration · Atmospheric

VVVVVV
Shared: Platformer · Precision Platformer · Difficult

