Games like o---o
Games like o---o include Vampire Survivors, Downwell, UFO 50, Geometry Dash, and Streets of Rage 4. We matched them by the tags players give o---o on Steam (Action, Arcade, Precision Platformer, 2D, and Futuristic): closest matches first, and among equally close ones the better-known games.

Vampire Survivors
Shared: 2D · Arcade · Indie

Downwell
Shared: Precision Platformer · Arcade · Action

UFO 50
Shared: Action · Arcade · 2D

Geometry Dash
Shared: 2D · Precision Platformer · Singleplayer

Streets of Rage 4
Shared: Action · 2D · Arcade

Timberman
Shared: Action · 2D · Arcade

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

Planes, Bullets and Vodka
Shared: Action · Arcade · Retro

Kung Fury: Street Rage - Ultimate Edition
Shared: Arcade · Action · Retro

Cyberhunt
Shared: Action · Arcade · Indie

A Dance of Fire and Ice
Shared: Arcade · 2D · Indie

Sixtar Gate: STARTRAIL
Shared: Action · Arcade · 2D

PAC-MAN™ Championship Edition DX+
Shared: Arcade · Action · Retro

LUFTRAUSERS
Shared: Arcade · Action · Indie

Retrowave
Shared: Action · Retro · Indie

Jump King
Shared: Precision Platformer · Action · 2D

SANABI
Shared: Action · 2D · Indie

Celeste
Shared: Precision Platformer · Indie · 2D

Trip to Vinelands
Shared: Action · Arcade · Indie

Exit the Gungeon
Shared: Arcade · Action · Indie

One Finger Death Punch
Shared: Action · Indie · 2D

Rogue Legacy 2
Shared: Arcade · Action · Indie

Broforce
Shared: Action · 2D · Indie

Shower With Your Dad Simulator 2015: Do You Still Shower With Your Dad
Shared: Arcade · 2D · Action