Use left and right arrows to move, hold down space to shoot. A further, more advanced version of this game is available here: https://scratch.mit.edu/projects/10217717/
Tutorial videos for making this available here: Part 1 http://www.youtube.com/watch?v=oiCgYgibqAM&list=PLkd_b3dcYaOQYnoFcLG6ClmViTTu0wOB5 Part 2 http://www.youtube.com/watch?v=pj3yUEpqUus&list=PLkd_b3dcYaOQYnoFcLG6ClmViTTu0wOB5 Part 3 http://www.youtube.com/watch?v=9s58mqxtIyk&list=PLkd_b3dcYaOQYnoFcLG6ClmViTTu0wOB5