Information below contains information that may ruin your enjoyment of discovering the game's secrets for yourself. Proceed at your own risk.
Gateway Engines are structures that make up the cores of each planet. They are spherical structures, with many pillars extending outward and up through the outer core layer of the planets. The pillars and sphere in the center use a different gravity than the planet does. When approaching any part of the engine, the player will be pulled and orientated to the surface of the structure and will be able to move "normally" along the surface. As gravity changes, the player will be noted by an acoustic signal, in order to reduce confusion.
As most pillars are not connected to the engine directly, the player will need to jump to be able to attach to the central sphere or build bridges using the Terrain Tool. There are two pillars that are connected and will easily allow the player to walk onto the outside of the sphere. On the inner part of the central sphere, there are three sides, the top and bottom, each of which will orientate the player to be able to run along to get around without issue.
When first approaching the Gateway Engine, it may be shielded if none of the Gateway Chambers has yet been activated on the surface. Once it is open, the player may enter the inside of the sphere. On one side are three raised platforms, similar to the Chambers, that will require a specific resource, marked with a specific symbol on top of each platform. Once the required item is provided, a Geometric Triptych will appear in the middle and the engine shield will reappear. The player must take the triptych up one of the three sides to the opposite platform. There, in the center, is a single platform with a slot for the triptych. Once it is placed, the engine will activate and reveal an Odd Stone, allowing teleporting to chambers on the surface, as well as to the satellite. Also, the shield will disappear, allowing the player to leave the engine.
Each Gateway Engine requires a specific resource to create a Geometric Triptych, which is required to activate the Engine. Only one of the resources is required for each planet. The Geometric Triptych is unique to each planet and can be created repeatedly. Note, that two triptychs are required: One to activate the engine, another one for the satellite.
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The Gateway Engines, much like the Gateway Portal satellite, provide oxygen once the player has entered the sphere that begins at the first holographic pattern that surrounds the core structure.