Feynman rules vs Duoku

This app introduces Feynman rules. You can get some understanding for Feynman diagrams. E is external point, V is vertex, P is propagator, and S is symmetry factor.

Your Sudoku skills are about to get tested. Four difficulty levels, a 3-mistake limit, and a ticking clock — every game is a race against yourself AND your friend. Share any puzzle with a friend and settle it on the same board. SHARE & COMPETE Every puzzle has a unique 4-character code. Send it to a friend, scan a QR code, or tap a link — you'll both play the exact same board. No more "I had an easier puzzle." Same grid. Same solution. Settle it. CHALLENGE YOURSELF Pick from Easy, Medium, Hard, or Expert. Each wrong move counts — three mistakes and it's game over, with a 60-second time penalty on every error. Use pencil notes to plan ahead, undo when you need to rethink, and push for a clean solve. TRACK EVERYTHING Your stats dashboard breaks down win rates, best times, average solve speeds, and mistake counts — all by difficulty. Chase personal records. Watch yourself get faster. BUILT FOR FOCUS No account required. No clutter. Autosave picks up exactly where you left off. Dark mode for late-night sessions. Haptic feedback on every tap. Designed to feel like it belongs on your phone. FEATURES • 4 difficulty levels — from beginner-friendly to expert-only • Pencil notes for tracking candidates • Undo and erase in one tap • Timer tracks every second • Smart highlighting for rows, columns, and matching numbers • Unplayed puzzles are served first • Continue any game, anytime • Full VoiceOver accessibility • Works offline