A few months ago I discovered a game called Lakeview Cabin. I really enjoyed playing it and showing it off to my friends to see what they could discover that I hadn't figured out yet; the game takes place on an incredibly tiny island, but it's jam-packed with interactions and puzzles that can keep you entertained for dozens of playthroughs. When we finally "solved" the game, I seriously jumped out of my chair in celebration. So rewarding!
Lone Survivor is sort of the same way, splayed out over a few hours; there are a few different ways to play through that game, and each one will give you a pretty different experience. Every time you beat the game, you'll get a different ending and come a little bit closer to the game's finale. 999 and The Stanley Parable also stand out to me as pulling this off really well, especially 999; beating that game was so incredibly satisfying. It was like solving a 30-hour Phoenix Wright case, and it required a lot of thought about the game's events. You have to know that game in order to beat it. I think it's really unique in that regard; a lot of puzzles in games, especially highly narrative-driven ones, can be somewhat brute-forced, but you really aren't very likely to solve 999 unless you actually know what you have to do.
I'm starting to gain a big appreciation for these short games that you can play over and over to unlock more secrets and have a different experience with each time. I'm playing through Ground Zeroes right now; that game is getting a ton of flack for being so short, but I've already sunk two hours into just one of the side missions, replaying it using different strategies to accomplish different goals. I'm starting to think about looking into speedrunning Super Metroid pretty soon too; talk about games that can replayed in radically different ways, Metroid should be one of the first that comes to mind. Zero Mission had, like, fifteen different recognized ways to play through it!
I'm curious as to what other "tiny sandbox" games might be out there that any of you might love-- games that you can really experiment with in order to gain a deep mastery of. Come to think of it, that might even be why Spelunky is so popular; it's basically distilled that whole process down into an easily-digestible 10-minute playtime. But I'm super-curious as to what else is out there, and what you've all accomplished. Do we have any Super Mario 64 speedrunners here? A lot of people swear by that game's controls and freedom of movement. How about Zelda 1? There are plenty of different ways to play through that game. Though those last two might even be a little too long to fit into a "tiny sandbox" definition. But, yeah. Stuff like that.
The only game I have ever really put any effort into speedrunning is Spelinky. Got pretty good until I burnt out on the game. I've been toying with the idea of running a glitched Ocarina of Time Any%, because I really love the run because of some of the stuff you do in it, but i'm waiting to get a capture card first so I can stream my attempts.
A certain game that I may or may not be developing is going to have elements of the whole short but different experience thingy. Mind you, the gameplay itself won't change up much. More the personal decisions and dialog and such.
999 is a great example. What I like about it and not about other similar games is that the story is built up for the fact that it requires multiple playthroughs. Other games that I think don't work as well are games like Heavy Rain. A lot of it is based on split second actions and playing it a second time, you're not forced to make a decision based on how you react to a given scenario but instead just play it out to do the opposite of what you last did. It takes away that impact that your actions cause.