The core playing rule
Bicycle requires following the led suit when able. A player who cannot follow may play any card. Highest trump wins a trick; without a trump, highest card of the led suit wins. The winner leads next.
Ask the permission question first
During a practice, pause before choosing a card. Find the relevant rule in the source and explain which cards are permitted. Do not decide that a play was legal simply because that card would win.
Then compare the played cards
Use the trick examples to compare a completed four-card trick. The tool sees only those four cards, not each player’s remaining hand. It can identify a winner for the entered cards but cannot prove that everyone followed suit correctly.