TwentyOne is a clean, focused blackjack basic-strategy trainer. Learn the mathematically correct play for every hand, then drill it until it's second nature — in a calm, minimalist interface with no ads and no clutter.
WHY TWENTYONE
Basic strategy is the proven, optimal way to play every blackjack hand. TwentyOne doesn't just show you a chart — it computes the correct play for your exact table rules and helps you commit it to memory through fast, focused practice.
THE STRATEGY CHART
• The complete chart for hard totals, soft hands, and pairs
• Color-coded for Hit, Stand, Double, Split, and Surrender
• Tap any cell to see the expected value behind every option
• Recomputes instantly when you change the rules
PRACTICE THAT STICKS
• Deal a hand, choose your action, and see the correct play right away
• Modes: Random, Hard Totals, Soft Hands, Pairs, and Most Missed
• "Most Missed" automatically resurfaces the hands you get wrong
• Track your accuracy, streak, and performance by hand type
PLAYS BY YOUR RULES
Real tables differ, and so does correct strategy. Configure:
• Number of decks (2, 4, 6, or 8)
• Dealer hits or stands on soft 17 (H17 / S17)
• Double after split, double rules, and late surrender
• Resplit aces, hit split aces, and more
The chart and every practice answer adjust automatically.
TWENTYONE PRO
Take your training further with a single one-time purchase — no subscriptions, no ads:
• Expected value on every hand — see the full EV breakdown behind your decision after each practice hand, not just in the chart
• Card Counting Trainer — master the Hi-Lo system with four focused drills:
– Card Values: flash through the +1 / 0 / −1 tags until they're instant
– Running Count: keep an accurate count as cards are dealt
– Deck Countdown: race through a full deck down to zero
– True Count: convert running count to true count on the fly
Everything else in TwentyOne is free.
MADE TO LOOK GOOD
• Minimalist design with crisp, simple cards
• Full light and dark mode
• Three app icons to choose from
• No ads, no accounts, no tracking — works offline for all training
TwentyOne is for study and entertainment. It teaches optimal decision-making and involves no real-money play and no wagering.
