How to play CALCTHRUM
Five numbers in each field. Five outer answers. One final puzzle in the centre.
How CALCTHRUM works
- Choose your operation. Plus, Times or Mixed, and one of five levels. Tap Start to reveal the numbers and start the clock. The symbol in each small blue field tells you which operation to use.
- Find the right number. Two numbers make a third. For 16 + 12 = 28, tap 28. The answer appears in the small blue field.
- Solve the centre. After five correct answers, those exact five numbers form the centre puzzle. Find the final answer and celebrate with confetti.
16 + 12 = 28
Operations
- Plus
- Find a sum of two other numbers outside and in the centre.
- Times
- Find a product of two other numbers outside and in the centre.
- Mixed
- Plus and Times appear outside. Each symbol shows the operation; use Plus in the centre.
Five levels
| Level | Plus: numbers up to | Times: factors up to |
|---|---|---|
| 1 | 20 | 8 × 8 |
| 2 | 40 | 9 × 9 |
| 3 | 100 | 10 × 10 |
| 4 | 180 | 12 × 12 |
| 5 | 300 | 15 × 15 |
Crossing out and hints
Long-press, right-click or press X to exclude a number as an answer only. You can still use it in calculations. Crossing out 77 does not change 40 + 77 = 117. “Hint” crosses out a wrong answer.
Clock and statistics
The clock starts when you tap Start and counts active playing time. Each wrong attempt immediately adds a 10-second penalty; final time, best time and average include it. Crossing out and hints add no time. In landscape, information and timer are on the left and the board on the right. It pauses in settings, help, legal notice and statistics, and while the tab is hidden. The final correct answer stops the clock and counts the round once. Statistics show lifetime and daily totals, best time, average time, wrong attempts, hints and recent rounds.
Language and sound
Open the gear at the top right. Choose Deutsch or English and Sound on or off. A correct answer reads its equation aloud, such as “16 plus 12 equals 28”. Times equations are read too. Fast Fish Audio recordings use Ben in German and Sarah in English. They are included in the game and work offline. No equations are sent to Fish Audio while you play.
Keyboard and new rounds
Tab moves between numbers and controls. Enter or Space chooses a number; X crosses it out. Arrow keys change operation and level. Escape closes settings and dialogs. “New puzzle” prepares another round. Tap Start to begin; “Next puzzle” follows the completed round.
Completing the round
The final correct answer starts the confetti celebration. Your final playing time appears in large type alongside the game information. With Sound on, the completion sound plays first, followed by the final equation. All six equations remain available. Reduced motion shows static confetti. Settings and game records stay on your device.