The board itself: twenty-one parts on numbered springs with a real Norton/Newton solver behind them, a drawer of spares, and a shop teacher who can see what you wired and turn a knob to prove it. Every circuit is a link — the bench reads its whole state from the URL.
Wire a real circuit on a spring-terminal board, with parts that really burn if you push them too hard, and a shop teacher who can see what you built. Free, no account.