It is nice to have a somewhat smaller example of using Trial!
Note on the trial version - I wasn't able to run the game with the quicklisp (shirakumo dist) version of Trial, and when I fetched it from github, it (1) had an additional non-quicklisp (yet) dependency - Shinmera/lru-cache, and (2) it just showed the white screen.
An older revision (commit 9d1acbb46bd57d30df7aa254eefa08c602f235cb or a2250cb6510ca490182278e125de6981eccccf10) worked.
Anyway, this game already has some nice graphics and gameplay, good luck with further developing :)
