When I ran the Web version in chrome the iframe turned black but downloading worked.
I also had problems in Edge (chromium). Works perfectly in Firefox.
It errors and refuses to continue at 'Press SPACE to start' or any of the 4 following 'Video playing event called's if there's no user input in a very short period prior to the call, even with the frame in focus. 'Press SPACE' shows at the same time as a video call, hence the lockup there.
Console error:
"Uncaught (in promise) NotAllowedError: play() can only be initiated by a user gesture. (anonymous) @runner.js:49"
You can get past it by clicking or pressing space constantly from end of loading til the game level appears, but I expect it'll happen again with any future video call.
Sorry for the late reply but this is the console (when the black screen appeared):
video_open failed. User must interact with the page before video with audio can be played. Attempting to play the video muted runner.js:44 Adding unmute listener runner.js:45 Done unmute listener index.html:1 Uncaught (in promise) AbortError: The play() request was interrupted by a call to pause(). runner.js:45 Calling onvideoframeupdate 2 index.html:753 focuscb:::blur event received Pause event has been registered for this frame
the AbortError was in red and linked to: https://developer.chrome.com/blog/play-request-was-interrupted