That's strange, it must be a bug. It's meant to restart after a few seconds. If you were to refresh the page it would probably work. I'll examine the server logs and see if I can reproduce the problem locally.
As for the multiplayer aspect, when I launched this game I expected more people would be drawn in due to the prospect of winning money (even though it's not much), so the map is designed for multiple players. I imagined that once all the gems were gone, people would go after the trophy, which would involve colliding with each other to erode the surrounding wall. I hoped the conflict between whether to cooperate or betray others would lead to interesting gameplay dynamics. As a single player game, it's a bit boring.
I'll be making a lot of changes in the coming weeks though. You'll notice I've already got rid of the ads. I'm going to get an artist to redo the graphics, and I'll add lots of new items like dynamite, doors, keys, levers, moving platforms, etc. There'll probably be a leaderboard too.