[bandwevil]

Firefox's cursor hiding breaks it, won't let you move the cursor, so don't enable it. Red circled cursor is your actual mouse position, grey circled one is the 'ingame' cursor that's blocked by walls. Move the red onto the grey to start.

[Maken]

FF 33.0 here, no problems so far, it even asks you politely if you want your cursor to be trapped when you enter the webpage.

[bjz_]

I found disabling the cursor lock on FF helped

[aaronem]

No trouble here. FF 31.1.0esr.