Thank you for your feedback and the recommendation. I really makes our day to hear people enjoy the game.
As for your questions:
1. You were right to enter the central building. There is an active puzzle at the top of the stairs with a purple laser. I realized after watching some people play that the laser is not sure visible, and because of the "new" color, it is not as noticeable when you walk up there. Definitely something to look at in the future. Thanks for mentioning it.
2. Your instincts were correct. All spheres must be lit up at the same time for the puzzle to be complete, however this is a bug we had in the version. We have already created a fix for it, but because it is not "game breaking" we are holding back on the deploy until after the voting ends, to give everyone the same experience when playing the game. The patch will be deployed soon after the voting ends (including a few other small bug fixes), so if you feel like playing it again, that might be a good time to give it a go. (There is also a secret to find as extra motivation if you haven't found it yet)
Thanks again for playing. We really appreciate it and your valuable feedback