  Generative Adversarial Networks (GANs) are an emerging form of indirect
encoding. The GAN is trained to induce a latent space on training data, and a
real-valued evolutionary algorithm can search that latent space. Such Latent
Variable Evolution (LVE) has recently been applied to game levels. However, it
is hard for objective scores to capture level features that are appealing to
players. Therefore, this paper introduces a tool for interactive LVE of
tile-based levels for games. The tool also allows for direct exploration of the
latent dimensions, and allows users to play discovered levels. The tool works
for a variety of GAN models trained for both Super Mario Bros. and The Legend
of Zelda, and is easily generalizable to other games. A user study shows that
both the evolution and latent space exploration features are appreciated, with
a slight preference for direct exploration, but combining these features allows
users to discover even better levels. User feedback also indicates how this
system could eventually grow into a commercial design tool, with the addition
of a few enhancements.
