Based on demo:
Standard behaviour for windows tooltips is for them to appear after a duration and not to disappear until you've moved the cursor *off* the widget. Currently the disappear as soon as you move the mouse.
Tooltips appear through modal dialogs (though behind them). There was a planet behind an 'ok' button, and this briefly confused me.
Tooltips for asteroids persist when you zoom in/out with the scrollwheel, and are relative to the cursor rather than the asteroid.
I couldn't finish the grey void level even though I had occupied all of the asteroids.
