Below is a real program. Every yellow box is a value you can change. Change one and the picture above changes straight away — no save, no reload, nothing to break.
The stage above is an element on this page. So is everything else. Turn this on and your two colour choices are used on the real page instead — the background and the accent colour. Reload and it is back to normal.
They are in order, easiest first, and the order never changes — challenge 7 is the same challenge tomorrow. One ticks itself the moment the code does what it asks, and stays ticked. Some of them fight each other on purpose: you cannot make every box pink and every box a different colour at the same time.
Your code is kept on this device, so switching language or closing the page does not lose it. Opening a friend's link never ticks anything off for you — their answer is theirs.