Same problem on Firefox on Linux :( For what it's worth, here's a stacktrace from the console:
[00:14:49.209] Error: successfully compiled asm.js code (total compilation time 238ms)
[00:14:51.321] "preload time: 2053 ms"
[00:14:51.564] Error: WebGL: enableVertexAttribArray: index -1 is invalid. That probably comes from a getAttribLocation() call, where this return value -1 means that the passed name didn't correspond to an active attribute in the specified program. @ https://dl.dropboxusercontent.com/u/4998298/ld/onelight.html:1990
[00:14:51.565] Error: WebGL: vertexAttribPointer: index -1 is invalid. That probably comes from a getAttribLocation() call, where this return value -1 means that the passed name didn't correspond to an active attribute in the specified program. @ https://dl.dropboxusercontent.com/u/4998298/ld/onelight.html:1993
[00:14:51.569] Error: WebGL: enableVertexAttribArray: index -1 is invalid. That probably comes from a getAttribLocation() call, where this return value -1 means that the passed name didn't correspond to an active attribute in the specified program. @ https://dl.dropboxusercontent.com/u/4998298/ld/onelight.html:1990
[00:14:51.569] Error: WebGL: vertexAttribPointer: index -1 is invalid. That probably comes from a getAttribLocation() call, where this return value -1 means that the passed name didn't correspond to an active attribute in the specified program. @ https://dl.dropboxusercontent.com/u/4998298/ld/onelight.html:1993
[00:14:51.601] uncaught exception: Assertion failed: E_OPENGL_ERROR == E_OK, at: src/FluxSpriteBatch.cpp,158,updateVBO at stackTrace@https://dl.dropboxusercontent.com/u/4998298/ld/onelight.html:1270
___assert_fail@https://dl.dropboxusercontent.com/u/4998298/ld/onelight.html:1704
Runtime.dynCall@https://dl.dropboxusercontent.com/u/4998298/ld/onelight.html:725
_emscripten_set_main_loop/Browser.mainLoop.runner@https://dl.dropboxusercontent.com/u/4998298/ld/onelight.html:6369