Doubling the limit to two hours would help a lot. Planetarium has no advertisements. The author hates them. I hate them too. If every puzzle-page I'd read had had an Amazon banner at the top, I probably would have packed it in about week two.
Planetarium is provided as true freeware, for love and ego points.
The rest of Dave Whiteland's web site is the same, by the way. I recommend a look around. He has a couple of Web comics, or graphic novels if you prefer. I anticipate, I keenly do. Also, he's into aikido.