The easiest way to try this is to use templates-cl-web-2d-game (one of a Roswell template).
Accoring to the document of the template-cl-web-2d-game, cl-web-2d-game itself is also installed. Then, you can execute the samples by the following (in REPL) and see them on https://localhost:5000/
by a web browser.
;; The output of each command is omitted.
CL-USER> (ql:quickload :cl-web-2d-game-sample)
CL-USER> (cl-web-2d-game-sample:start)
- eshamster ([email protected])
Copyright (c) 2016 eshamster ([email protected])
Licensed under the LLGPL License.