A photo-realistic right hand holding a black stylus glides across a 4×4 number grid on a desk-tone paper background. Tap any two cells that SUM TO 10 or are EQUAL — the hand smoothly moves between them, taps each (audible tick feel via animation), then draws a red diagonal strike-through. After each pair, the hand glides back to a fixed resting position off the grid. 4 pairs to win. Locked to 9:16 mobile aspect ratio — looks like a phone regardless of viewport. Single self-contained HTML (~114 KB) with the hand photo base64-embedded — no external assets.