Cardinal

Read the set-builder clues, then drop each element into the Venn region where it belongs — or tally exactly how many satisfy the condition.

How to play

Each puzzle gives a collection of elements and conditions written in set-builder notation over two or three sets. In Sort mode you place every element in its correct Venn region; in Count mode you work out how many elements meet a given rule.

• Drag each element into the region (A, B, C, an intersection, or outside) that matches the membership rules.
• Switch to Count mode to answer combinatorics-style 'how many' questions instead of sorting.
• Use Hint if you're stuck and Check to test your current arrangement.
• Satisfy every condition to solve the puzzle.

Controls

• Desktop: drag elements between regions with the mouse; click Sort/Count, a difficulty, and Daily/Practice in the bar.
• Phone & tablet: drag elements with your finger and tap the buttons — touch is fully supported.

Tips & strategy

• Translate each clue into plain membership first: 'in A but not B' is the A-only slice.
• Handle intersections last — pin down the unambiguous A-only, B-only and outside elements first.
• In Count mode, watch for overlap so you don't double-count elements that belong to two sets.

What you'll learn

Cardinal turns set theory and combinatorics into hands-on Venn-diagram sorting and counting.

• Skills: set theory, combinatorics, Venn diagrams, counting
• Best for: roughly grades 9–12 (ages 14+)
• For parents & teachers: set theory and counting.

About Cardinal

Cardinal turns set theory and combinatorics into hands-on Venn-diagram sorting and counting. It's an original, free browser game offering Sort and Count modes, three difficulties, and both daily and practice puzzles.

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