Adapted by abin, 2026-10-26, from https://github.com/phoboslab/underrun (MIT License, copyright 2018 Dominic Szablewski; see LICENSE.md). The music engine is a modified Sonant-X (zlib license; notice retained at the top of the Sonant-X section in underrun.js). The source files are concatenated unminified in the order given by the upstream build.sh instead of being minified, so underrun.js is the editable source. An empty timer callback in the intro terminal (which browsers would otherwise evaluate as a string) was replaced with a no-op function. A ready signal for the TapGameHub player, same-origin CSP, noindex and a credit line were added. No gameplay, graphics or audio changes.
