Games like Signal Simulator
Games like Signal Simulator include Kerbal Space Program, Five Nights at Freddy's, No, I'm not a Human, MiSide, and Alien: Isolation. We matched them by the tags players give Signal Simulator on Steam (Simulation, Indie, Psychological Horror, Space, and Aliens): closest matches first, and among equally close ones the better-known games.

Kerbal Space Program
Shared: Simulation · Space · Sandbox

Five Nights at Freddy's
Shared: Horror · Psychological Horror · Indie

No, I'm not a Human
Shared: Psychological Horror · Indie · Horror

MiSide
Shared: Psychological Horror · Horror · First-Person

Alien: Isolation
Shared: Horror · Aliens · Space

Outlast
Shared: Horror · Psychological Horror · First-Person

Mouthwashing
Shared: Psychological Horror · Indie · Horror

Lethal Company
Shared: Horror · Psychological Horror · First-Person

Poppy Playtime
Shared: Horror · Psychological Horror · Indie

Lobotomy Corporation | Monster Management Simulation
Shared: Psychological Horror · Simulation · Horror

Layers of Fear (2016)
Shared: Psychological Horror · Horror · Indie

Dead Space
Shared: Horror · Space · Psychological Horror

Universe Sandbox
Shared: Simulation · Space · Sandbox

Breathedge
Shared: Space · Indie · Sandbox

Universe Sandbox
Shared: Simulation · Space · Indie

Iron Lung
Shared: Psychological Horror · Indie · Horror

Space Engineers
Shared: Simulation · Space · Sandbox

[Chillas Art] The Convenience Store
Shared: Indie · Psychological Horror · Simulation

Spaceflight Simulator
Shared: Simulation · Space · Sandbox

Firework
Shared: Indie · Horror · Psychological Horror

Outlast 2
Shared: Psychological Horror · Horror · First-Person

Five Nights at Freddy's 2
Shared: Horror · Psychological Horror · Indie

Outer Wilds
Shared: Space · Indie · Atmospheric

Five Nights at Freddy's 3
Shared: Horror · Psychological Horror · Indie

