  On the sad occasion of contributing to the memorial volume ``Fundamental
Interactions'' for my teacher Wolfgang Kummer I decided to recollect and extend
some unpublished notes from the mid 90s when I started to build up a string
theory group in Vienna under Wolfgang as head of the particle physics group.
His extremely supportive attitude was best expressed by his saying that one
should let all flowers flourish. I hope that these notes will be useful in
particular in view of the current renewed interest in heterotic model building.
The content of this contribution is based on the bridge between exact CFT and
geometric techniques that is provided by the orbifold interpretation of simple
current modular invariants. After reformulating the Gepner construction in this
language I describe the generalization to heterotic (0,2) models and its
application to the Geometry/CFT equivalence between Gepner-type and
Distler-Kachru models that was proposed by Blumenhagen, Schimmrigk and
Wisskirchen. We analyze a series of solutions to the anomaly equations, discuss
the issue of mirror symmetry, and use the extended Poincar\'e polynomial to
extend the construction to Landau-Ginzburg models beyond the realm of rational
CFTs. In the appendix we discuss Gepner points in torus orbifolds, which
provide further relations to free bosons and free fermions, as well as - simple
currents in N=2 SCFTs and minimal models.
