We investigate the triangle singularity f = x a + y b + z c , or S = k[x, y, z]/(f ), attached to the weighted projective line X given by a weight triple (a, b, c). We investigate the stable category vect-X of vector bundles on X obtained from the vector bundles by factoring out all the line bundles. This category is triangulated and has Serre duality. It is, moreover, naturally equivalent to the stable category of graded maximal Cohen-Macaulay modules over S (or matrix factorizations of f ), and then by results of Buchweitz and Orlov to the singularity category of f .We show that vect-X is fractional Calabi-Yau whose CY-dimension is a function of the Euler characteristic of X. We show the existence of a tilting object which has the shape of an (a − 1) × (b − 1) × (c − 1)-cuboid. Particular attention is given to the weight types (2, a, b) yielding an explanation of Happel-Seidel symmetry for a class of important Nakayama algebras. In particular, the weight sequence (2, 3, p) corresponds to an ADE-chain, the Enchain, extrapolating the exceptional Dynkin cases E 6 , E 7 and E 8 to a whole sequence of triangulated categories.