Games like External-Dimension: Mainframe
Games like External-Dimension: Mainframe include SANABI, Dust: An Elysian Tail, Cave Crawler, Mark of the Ninja, and Gravity Circuit. We matched them by the tags players give External-Dimension: Mainframe on Steam (Side Scroller, Action, 2D Platformer, Platformer, and 2D): closest matches first, and among equally close ones the better-known games.

SANABI
Shared: Action · 2D Platformer · 2D

Dust: An Elysian Tail
Shared: Action · Platformer · 2D

Cave Crawler
Shared: Side Scroller · 2D Platformer · Platformer

Mark of the Ninja
Shared: Platformer · Action · Side Scroller

Gravity Circuit
Shared: Action · Platformer · 2D

Rogue Legacy
Shared: Platformer · Action · 2D

Skul: The Hero Slayer
Shared: Action · 2D · Indie

Blasphemous 2
Shared: Side Scroller · 2D Platformer · Fantasy

Super Meat Boy
Shared: Platformer · 2D Platformer · 2D

Anomaly Agent
Shared: Side Scroller · 2D Platformer · Platformer

Shovel Knight: Treasure Trove
Shared: Platformer · Action · 2D

Broforce
Shared: Action · 2D · Platformer

ICEY
Shared: Action · Side Scroller · 2D

Momodora: Reverie Under The Moonlight
Shared: Side Scroller · 2D Platformer · 2D

Smilemo
Shared: Action · Platformer · 2D Platformer

Thomas Was Alone
Shared: Side Scroller · Platformer · 2D Platformer

Katana ZERO
Shared: Action · Platformer · 2D Platformer

Deadlight
Shared: Action · Platformer · Side Scroller

20XX
Shared: Action · Platformer · 2D Platformer

NINJA GAIDEN: Ragebound
Shared: Action · 2D Platformer · Platformer

Hollow Knight
Shared: Platformer · 2D · Indie

Eastern Exorcist
Shared: Action · Side Scroller · 2D

Rayman® Legends
Shared: Platformer · Action · 2D

Zombotron
Shared: Action · 2D · Platformer

