Games like String Theory
Games like String Theory include ICEY, Your Only Move Is HUSTLE, DJMAX RESPECT V, Hades, and NieR:Automata™. We matched them by the tags players give String Theory on Steam (Action, Music-Based Procedural Generation, Casual, Rhythm, and Simulation): closest matches first, and among equally close ones the better-known games.

ICEY
Shared: Action · Side Scroller · Hack and Slash

Your Only Move Is HUSTLE
Shared: Action · Spectacle fighter · Simulation

DJMAX RESPECT V
Shared: Rhythm · Casual · Action

Hades
Shared: Action · Action Roguelike · Hack and Slash

NieR:Automata™
Shared: Action · RPG · Hack and Slash

Music Racer
Shared: Music-Based Procedural Generation · Rhythm · Action

Vampire Survivors
Shared: Action Roguelike · Casual · Action

Skul: The Hero Slayer
Shared: Action · Action Roguelike · Indie

Muse Dash
Shared: Rhythm · Casual · Anime

A Dance of Fire and Ice
Shared: Rhythm · Casual · Action

Death Must Die
Shared: Action · Action Roguelike · RPG

Bladed fury
Shared: Action · Casual · RPG

Hades II
Shared: Action · Action Roguelike · Hack and Slash

Hi-Fi RUSH
Shared: Action · Rhythm · Hack and Slash

Beat Hazard
Shared: Music-Based Procedural Generation · Rhythm · Action

Eastern Exorcist
Shared: Action · RPG · Side Scroller

The Vagrant
Shared: Action · RPG · Side Scroller

Touhou Mystia's Izakaya
Shared: Casual · Simulation · RPG

Melody's Escape
Shared: Music-Based Procedural Generation · Rhythm · Action

Plebby Quest: The Crusades
Shared: Casual · Action · Simulation

Book of Yog Idle RPG
Shared: Simulation · Casual · Action

Dead as Disco
Shared: Rhythm · Spectacle fighter · Action

鬼谷八荒 Tale of Immortal
Shared: Simulation · Action · RPG

BlazBlue Entropy Effect
Shared: Action · Action Roguelike · 2D