To qualify as potentially life-friendly, a planet must be relatively small (and therefore rocky) and orbit in the "habitable zone" of its star, which is loosely defined as a location where water can exist in liquid form on a world's surface.
When telescope technology improves, other factors will be considered as well, such as the planet's atmospheric composition and how active its parent star is.
Click on screen to startGame
Left & Right Arrows to rotate space ship
Up Arrow to shoot rocket
Space to thrust