Abstract: GLSM quasimap theory is a curve-counting theory of Gromov-Witten type associated with a smooth variety and a regular function on it. Conceptually, GLSM reflects the geometry of the critical locus of the function. In a joint work with Melissa Liu we define and compute certain generating functions of GLSM invariants called I-functions and central charges. In the talk I will explain what they are, how to relate them with the usual quasimap invariants, and how to compute the generating functions using a version of Fourier transform.