Edabit

The homepage demonstrates the scale of its approach with a small addition function. That makes it a useful candidate for practising one piece of syntax at a time. Try explaining the expected input and output before changing the code. Use larger projects elsewhere when you want to practise how many functions fit together. The current FAQ says all challenges are free and that new memberships are no longer sold. It also says you may revisit completed challenges, although overall progress cannot be reset. The site is designed primarily for desktop use with a physical keyboard.