21 vs HamiLoop

Hit 21. Don't bust. Claim falling cards, stack smart, and clear every slot. Easy to learn, impossible to master.

HamiLoop: Draw one loop. Pass through every square on the grid exactly once. That's the whole idea behind HamiLoop, and it's harder than it sounds. What looks like a simple rule turns into a real puzzle once the grid grows, and figuring out the right path can take real thought. Grid sizes vary a lot, so difficulty varies with them. Some puzzles are solved in a couple of moments, others take much longer and require some careful planning. With 150,000 preloaded levels, you can pick a size and difficulty that suits your mood, and a new difficult puzzle is added every day if you're after something tougher. There are no timers and no countdowns anywhere in the app, so every puzzle can be worked through at your own pace. Each puzzle is presented with clean, colorful visuals, though the colors are purely decorative and don't affect the solving itself. If you like tackling more than one thing at a time, you can keep several levels open in parallel, so an easier puzzle is always there when you want a break from a harder one. Alongside the daily challenge, an extra hard puzzle is released once a week for players looking for something tougher still. The core idea of the game is inspired by Hamiltonian cycles, a well known concept from graph theory, giving the puzzle a solid mathematical foundation beneath its simple rule.