Games like Space Simulation Toolkit

"Medieval Engineers" is a sandbox game set in the medieval era, focused on realistic engineering principles. Players can build various structures, such as castles and siege machines, using a variety of materials. The game also features a physics-based destruction system, allowing for realistic deconstruction and demolition of creations.

The Sapling is a simulation game where you design your own plants and animals, and put them in a world together. Or you turn on random mutations, and see what evolution does to your ecosystem!

Space Engineers 2 offers a fully playable survival experience where you can explore diverse biomes, mine resources, and build structures on destructible terrain. Manage your engineer’s health, power, and resources while crafting tools and establishing basic production chains. Utilize advanced building tools like holographic projections to design and construct ships, rovers, and bases as you begin colonizing the Almagest system.

Ultimate Epic Battle Simulator 2 is a sandbox-style simulation game that allows players to create and control large-scale battles with various units and environments. The sequel brings improved graphics, more detailed physics, and a wider range of units and customization options compared to the original game. Players can create their own scenarios or play through pre-made battles, testing their strategic skills and watching epic battles unfold.

"Prehistoric Kingdom" is a zoo management simulation game where players build and manage a park for extinct animals. Utilize creative tools to design habitats and infrastructure, and breed over 20 species of prehistoric wildlife. Discover new creatures and genetic skins while ensuring the safety and resources for guests, animals, and staff.

"KitHack Model Club is a simulation game that allows 1-2 players to build and customize RC vehicles in a multiplayer setting. The game features physics-based mechanics, encouraging players to make every design decision count. With numerous parts, paint, and decals to choose from, create and race your unique vehicles in this ultimate model-building platform."

"Hometopia is a simulation game in early access, allowing 2-4 players to cooperatively build and design homes with career progression. While it has spectacular game mechanics and good graphics, it is currently hampered by optimization issues and bugs. The developers emphasize Hometopia as an ongoing, creative platform for players and are responsive to feedback."

"Juno: New Origins Complete Ed." is a 3D aerospace sandbox game that allows players to build and test their own custom vehicles with realistic physics. The newly added Career Mode lets players run their own aerospace company, completing hand-crafted and procedural contracts to earn money and unlock new technology. With a tech tree, interactive tutorials, and the ability to share creations online, this game offers countless hours of creative and challenging gameplay.

Universe Sandbox is a physics-based space simulator that allows players to create, destroy, and interact on an unparalleled scale. Experience realistic gravitational pull, collisions, and stellar phenomena as you build and manage your own universe. With accurate models of known celestial bodies and the ability to create your own, this game offers a sandbox for both education and entertainment.

"Plasma" is a single-player Simulation game that allows players to build and control their own devices using a visual programming tool. With a focus on creativity and engineering, players can construct robots, factories, game worlds, and more, and share their creations with the community through the Steam Workshop. However, the game's gameplay has received poor reviews, with completion taking around 30 hours.