Randall Munroe’s popular and (by now) venerable geek webcomic XKCD has been known to make “interactive posts” sometimes, little apps or even games that readers can play with. Lately there’s been two in particular of these, both focused towards space exploration: Gravity, made to promote Munroe’s recent book What If? 2, and Escape Speed, created in celebration of SpaceX’s recent launch, or at least celebrating the idea of it, since its actual fact turned out to not be so great.
Both games are much larger than they seem to be at first, offering a vast amount of void to whoosh around and entertaining planets to find within all that space. Gravity is mostly just for exploration, while Escape Speed is more like an actual game, starting your ship off with very modest capabilities that grow in power as you collect upgrades, which are gray circles with stars on them. You can find at least one upgrade on or near most objects out in space, and sometimes several.
There’s a lot to find, especially in Escape Speed, which also has a lot of minor collectables to locale, which it’ll track between runs. Escape Speed even has a couple of objectives to complate: locating the Hyperdrive, which requires finding out what happened to the map of Boston on Subway Planet, and eventually escaping from the huge crystal sphere that contains the game universe. Both games have enough going on that they have giant pages on the Explain XKCD fan wiki revealing their secrets. In case you can’t be bothered to discover them yourself, here’s the one for Gravity, and here’s the one for Escape Speed.
XKCD 2765 Escape Speed – FAQ