A hook swings back and forth with a Dudu on it. Tap to let go and it drops onto the top of the pile. Land it close to the one below and it stays; too far off and it slides away (you have three lives). Land it dead center for a Perfect, and a few Perfects in a row pull the tower back up straight. The tower leans the way you keep missing and sways more as it grows. If the Dudus above any one of them hang too far off its middle, everything above it comes down. Higher up the hook swings faster and the wind starts to blow. Every outfit plays differently. Chubby Chefs and Puffers are wide and easy to stand on. The Astronaut falls slowly and drifts the way the hook was swinging. The Ninja is narrow, but Perfect is twice as easy. Knights land with a thump and calm the tower. Now and then the Fortune God comes along: 5 extra points and a life back. The Dudus' faces follow the tower: happy when they land, shy when they're off, all worried when it wobbles. Everyone you stack goes into your Dudu album. One Dudu is about half a meter tall, and the heights you pass are real: a basketball hoop 3.05 m, a giraffe 5.5 m, the Hollywood sign's letters 13.7 m, Christ the Redeemer 30 m, the Statue of Liberty 46 m, the Leaning Tower of Pisa about 56 m, Big Ben 96 m. The Dudus are the Y Build app's own drawings. The sky, city, clouds and space behind them were drawn by AI (no text, no Dudus). Sound effects are by Kenney (CC0), the background music is AI-generated, and the Dudu's squeak is synthesized.