The player flies a spaceship through colored pencil illustrated backgrounds, dodging obstacles and collecting stars to open wormholes into the next of fifty-five levels. The ship heads towards wherever the screen is tapped, making the gameplay simple and intuitive. The player must develop skills to navigate around and between a wide range of obstacles such as wildly zigzagging aliens, burning fire, and schooling fish. What makes the game truly unique is the quality of the illustrations and soundtrack, as well the complexity of the gameplay. The flavor of the game is upbeat and whimsical. As Space Girl collects stars she shouts "Nice!" or "Wow!"
In Space Girl, the levels are divided into four categories: outer space, water world, alien encounters, and underwater aliens. Each comes with its own background illustrations, obstacles, and creatures. Between levels, a series of beautifully colored drawings tells the story. In outer space, hearts break when bumped while gas giants attract smaller objects with their gravity. In the water world, glass bottles burst apart, becoming more dangerous. Rapidly multiplying bacteria inhibit movement. In the alien levels, four types of aliens zoom around collecting their own blue stars. They each have a characteristic flight style. When there are green and purple aliens, exploding asteroids, gas giants, and flames all on the screen at once, things can get pretty complex.
The ship shields are damaged by bumping an obstacle and replenished by collecting a star. When the shield fails, the ship explodes.
Other features include a random play mode and achievements.