Chusho Crest

Chusho Crest brings mathematical knot theory to your fingertips. Trace loops over photos of real chains, rings, or knotted cords and let the app instantly compute the invariants that define them — writhe, linking number, tricolouring count, determinant, and more. Match your tracings against a curated table of 20 classic knots and links, from the humble unknot to the celebrated Borromean rings. Learn through nine structured lessons that take you from your first crossing all the way to mirror images and Brunnian links. Then test your understanding with six drill types: identify crossing signs, compute linking numbers, colour diagrams by the Fox rule, spot Reidemeister moves, decide whether loops are splittable, and name the diagram in front of you. Every drill is scored, timed, and saved so you can watch your skills grow session by session. Save your own traced tangles to the Notebook, complete with computed invariants and personal notes. Revisit them alongside your full drill history whenever you like. Chusho Crest works entirely offline with no account, no subscription, and no data leaving your device. Whether you are a mathematics student meeting knot theory for the first time, a jewellery maker curious about the formal structure of interlocking rings, or simply a curious mind drawn to elegant patterns, Chusho Crest gives you the tools to explore one of the most beautiful corners of pure mathematics.