Accrete

A growth-arena game (the agar.io family) themed as cosmic accretion. You're a forming body drifting a field of stardust. Hold and drag anywhere to steer toward your finger; absorb dust and any body lighter than you (its centre must fall inside you) to gain its mass. Mass sets size and size sets speed — the bigger you grow, the slower you move and the bigger a target you are. Anything ringed red can swallow you (flee it); anything ringed green you can swallow. Grow as massive as you can.