Thank you so much!
Yeah, the .exe is more stable generally, but the web version should still work. To draw the wall, hold down the draw button (LMB/RT) then trace a loop, and then release the button either after the draw line has intersected itself, or when you've returned to where you started drawing the line from. We've realised that this can be a bit confusing from a first-person perspective, so any tips on how the wall drawing could have been explained or tutorialised better are sincerely appreciated!