Thomas Was Alone is a puzzle platformer about friendship and a remake of the Flash game with the same name. The player takes control of a red shape that represents a string in a programming environment. The goal is to move through an abstract environment to complete 100 levels by moving and jumping. A level is completed when the shape is moved to a white outline of its form.
The game's story follows Thomas, a red shape who feels alone and doesn't know his purpose. As he moves around and jumps, other shapes appear, each with their own abilities and personalities. The player must navigate through levels, switching between shapes to control them individually. The narration explains the thoughts and emotions of the shapes, building their personalities through their cooperation and interactions.
The gameplay is straightforward but engaging, with a focus on puzzle-solving and exploration. Levels can be completed by moving all shapes to their correct positions, and some levels feature multiple shapes that must work together. The game's visuals are simple yet expressive, with each shape's design reflecting its personality and abilities.
A DLC expansion called Benjamin's Flight was released for the PlayStation 4 console, introducing new content to the game.