TwentyOne Lens

TwentyOne Lens is an educational probability workspace for exploring the mathematics of blackjack-style card decisions. Build two visible hands by choosing a suit and rank, then inspect how the remaining single deck changes the possible outcomes. The app calculates directly from the cards you enter—without random estimates or invented results. FEATURES • Fast suit-first card selection • Two editable hands with duplicate-card prevention • Correct Ace handling as 1 or 11 • Exact probability of busting or remaining safe on the next card • Hit, Stand and eligible Double comparisons • Per-rank probabilities and remaining-card counts • Safe, Bust and Wished Card filters • Remaining deck composition by suit • Clear calculation assumptions inside the app • No account, advertising or data collection PROBABILITY MODEL TwentyOne Lens uses a standard 52-card single deck. Every entered card is…