Use the arrow/WASD keys to move, and press space to launch a rock towards the mouse. Use turbo mode if the player gets too far off the screen (they'll have to come back eventually). Use if laggy: https://sulfurous.aau.at/#269059703
Made as an explanation/example for how to implement gravity with multiple planets for @Theoul's cool project (being updated): https://scratch.mit.edu/projects/266190868 Technically gravity should cause the planets to move closer to each other, but let's just ignore that. An explanation for the physics is inside the project.