Ok, so I just bought Tidalis. It was inevitable
I loaded it up, entered the serial key (Steam), and went directly to the first tutorial as suggested by the game. The goal: Click a block. So I did, annnnd... nothing happened.
I got a "glowing M" in the bottom-right corner of the block, if I recall. This would toggle on and off if I kept clicking. After clicking madly, I even got a "glowing M4" symbol to toggle on and off. But no stream, and no way to complete the level.
Restarting the level via admitting defeat (!) did not help. But restarting it via the tutorial menu, did.
So what's the deal? Did I press some key or activate some special mode without knowing it? Was it the shift+tab to get rid of the Steam overlay? It was a confusing start!
Edit: Having played a few more tutorials now, I feel I had better point out that no, I was not right-clicking. It was the left mouse button that did this behaviour.