Everything is done with the mouse. For additional instructions, or if you have no idea what to do, click on "Notes and Credits" in the menu. If you wish to enbroider your amazing time in silk and gold, there's always a comments section. Just remember to post the speed and interval too. Reading the actual notes and credits below may help too for a select few issues.
If there's any bugs, post below. And as said at the top of the menu, if no buttons show up, you might have to press the green flag again. Something that actually wasn't mentioned in the in-game notes 'n credits: The values that you input SHOULD be saved for the next round unless you change them. Thus, you don't have to set the same values over and over again each time you die. Get bored of a level? There's a big juicy red wall for you to run into on all four sides. Touch at your own risk.