7-bridge puzzle that changed math. In the 1700s, the people of Königsberg tried to walk through their city by crossing each of its seven bridges exactly once without repeating any. No one could do it—and no one knew why. Then came Leonhard Euler. Instead of tackling the city’s layout directly, he reframed the problem completely: turning bridges into lines, and landmasses into points. Using logic, symmetry, and a whole new kind of math, he cracked the puzzle—and unknowingly sparked the creation o