The hand-drawn sprites are a welcome sight, and the music matches the aesthetic well. The gameplay could be more exciting, though. Maybe the gamma ray could shoot from a random height rather than just the top. The clouds also don't seem to do anything; if they made the player move slower, then they could become a pretty interesting obstacle. Another thing that could fix up the gameplay is some sounds. It might sound ridiculous, but audio can make even a simple game feel good to play.