Games like Protecto
Games like Protecto include People Playground, Garry's Mod, Bloons TD 6, Plants vs. Zombies GOTY Edition, and Plague Inc: Evolved. We matched them by the tags players give Protecto on Steam (Casual, Outbreak Sim, Sandbox, Puzzle Platformer, and Tower Defense): closest matches first, and among equally close ones the better-known games.

People Playground
Shared: Sandbox · 2D · Physics

Garry's Mod
Shared: Sandbox · Casual · Physics

Bloons TD 6
Shared: Tower Defense · Casual · Singleplayer

Plants vs. Zombies GOTY Edition
Shared: Casual · Tower Defense · 2D

Plague Inc: Evolved
Shared: Outbreak Sim · Casual · Indie

Bloons TD 5
Shared: Tower Defense · Casual · 2D

Zup! 3
Shared: Casual · Indie · 2D

Kingdom Rush - Tower Defense
Shared: Tower Defense · Casual · 2D

Zup!
Shared: Casual · Indie · 2D

Totally Accurate Battle Simulator
Shared: Sandbox · Physics · Indie

Zup! 2
Shared: Casual · 2D · Indie

Human Fall Flat
Shared: Sandbox · Puzzle Platformer · Physics

Defy Gravity Extended
Shared: Puzzle Platformer · Indie · 2D

Zup! S
Shared: Casual · 2D · Indie

Goat Simulator
Shared: Sandbox · Casual · Physics

Zup! F
Shared: Casual · Indie · 2D

Zup! X
Shared: Casual · Indie · 2D

Happy Wheels
Shared: Sandbox · Physics · Indie

Zup! 8
Shared: Casual · 2D · Indie

Game Dev Tycoon
Shared: Casual · Indie · 2D

LIMBO
Shared: Puzzle Platformer · Indie · 2D

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

Kingdom Rush Frontiers - Tower Defense
Shared: Tower Defense · 2D · Casual

Noita
Shared: Sandbox · Physics · Indie