Games like The Red Reactor
Games like The Red Reactor include Once Human, ARK: Survival Ascended, ARK: Survival Evolved, Satisfactory, and Rust. We matched them by the tags players give The Red Reactor on Steam (Action, Indie, Strategy, Building, and Open World): closest matches first, and among equally close ones the better-known games.

Once Human
Shared: Action · Open World · Building

ARK: Survival Ascended
Shared: Open World · Base Building · Building

ARK: Survival Evolved
Shared: Open World · Building · Crafting

Satisfactory
Shared: Base Building · Open World · Building

Rust
Shared: Open World · Crafting · Building

Sons Of The Forest
Shared: Open World · Base Building · Building

Palworld
Shared: Open World · Indie · Crafting

Medieval Dynasty
Shared: Building · Crafting · Open World

Factorio
Shared: Base Building · Strategy · Crafting

Kenshi
Shared: Open World · Crafting · Action

Schedule I
Shared: Open World · Action · Crafting

Manor Lords
Shared: Strategy · Base Building · City Builder

Dwarf Fortress
Shared: Strategy · Base Building · Building

Raft
Shared: Open World · Building · Crafting

Valheim
Shared: Open World · Building · Crafting

The Forest
Shared: Open World · Building · Crafting

Thronefall
Shared: Strategy · Action · City Builder

Kingdoms and Castles
Shared: Strategy · City Builder · Building

TerraTech
Shared: Building · Open World · Action

Scrap Mechanic
Shared: Building · Open World · Crafting

Colony Survival
Shared: Building · Base Building · Strategy

Against the Storm
Shared: Strategy · Building · Base Building

Dyson Sphere Program
Shared: Building · Base Building · Open World

Craft The World
Shared: Building · Crafting · Strategy