In my talk, I will delve into the 2d N=(0,2) and N=(0,4) theories, derived from class S theories compactified on S2 with a topological twist. My presentation will focus on elucidating the TQFT structure on Riemann surfaces. Furthermore, I will discuss the connection between the left-moving sector of the (0,2) theory and the chiral algebra of the 4d N=2 theory. Specifically, I propose that the (0,2) elliptic genus of a theory in this class can be expressed as a linear combination of characters from the chiral algebra. This talk is based on a collaboration with Yiwen Pan and Jiahao Zheng [arXiv:2310.07965].