WASD to move, mouse to shoot. Shift to aim farther, but it slows you down. Standing on the point for 144 frames (4.8 seconds at 30FPS) captures it. If you stand off it for more than 1 second, your capture progress is reset.
This is a highly efficient base for shooter engine. Unfortunately, using vector graphics is not possible for a system like this. Using them drops framerate dramatically in higher resolutions (a limitation of Adobe Flash) and the individual objects on screen can lag behind each other, so they don't all move together (a limitation of Scratch). This engine uses a per-frame rendering technique that prevents desync in the various objects on screen. That means it also manually calculates all movement and hit detection, requiring lots of manual script implementation. Many of Scratch's convenient built-in functions will not work. There are several sprites and variables I left in from early versions of the engine for archival pursoses.
