Press the green flag. After that, move the mouse around and see what you can discover if you press the mouse in different parts of the stage. Can you resist the urge to look inside for hints?
I began by thinking about the question "what kind of secret would I like to reveal?" I'm not sure if I share the right amount of information in the instructions + while playing. I want those playing to discover the features, though is there enough to start from? How is the timing? [intentionally minimal notes for hidden factor!]