I am curious what games would fit this criteria:

1. Must be fun to play if you only have 10-15 minutes.
2. Said play should be complete: Those 10-15 minutes of play should not significantly affect future play sessions. (For example, an RPG is not what I am looking for.)
3. Must not depend on anything external to the game; in particular, must not depend on Internet access or another human player being available.

I can think of 2 games I own from this site that meet these criteria:
1. Crimzon Clover: Training mode and Time Attack are great for short playing sessions. (Time Attack is only 3 minutes long.)
2. Ys Origin's extra modes. Unfortunately, you need to beat the game normally with all three characters to unlock these modes, and the main game does not fit the criteria.

I'm not very good at tracking gaming time but :

a) Symphony is a cool shooter that lasts as long as the mp3 you decide to use.

b) Some Creeper World maps can be short-ish. I'm not sure 15 min suffices though.

c) Moon Commander (a top-down Worms-like) is also cool, and also provide some short maps and, if I remember well, parametrable skirmishes.

d) Worms itself is excellent in short bursts.

e) Door Kickers missions don't last very long either.

f) Toys-like games like Little Inferno can be as short as you want. They are a bit progression-based, though.

g) World of Goo can levels still also be completed in a short time.

FTL and Hotline Miami can be deceptively long. An hour or two easily for FTL. And lots of (joyous) restarts make Hotline eat up time more than its smallish levels would let you think. I also wonder, in retrospect, how long an early SpaceChem level used to take, but it may be worth testing.

Also :

h) Papers Please. It dos have some progression continuity, but its stressful workdays are pretty short.

Pocket snooker!

Race the Sun
Risk of Rain
These two are exactly what you describe, and a bunch of people swear by them. I hate hate hate hate hate both (fucking dumbass no-progress permadeath shit) so much that I think less of people who like either. (This is not meant as an insult, it's just, idunno, people must have downloaded some other game files through a wormhole from a parallel world or something. cactus (of Hotline Miami fame) once made a free troll game which randomized unfair fuckery and inflicted in on the players, then watched the fallout. This is exactly what it feels like.)

Uplink has a continuous campaign, but can be played 15 minutes at a time. The hacking runs themselves are very short.

Spacechem, TIS-100 and Sokobond are puzzle games. The puzzles are unlockable but standalone.

Defender's Quest has a continuous campaign consisting of short levels. 15 minutes is the longest I've held against infinite creeps, which is way longer than any single level. Party composition and equipment carries over, though.

I don't know how long a playthrough of Long Live the Queen takes, but it's fairly short. Probably not 15 minutes though. It's a learn-by-dying choose-your-own-adventure, which means extensive note-taking is needed to progress between sessions, but each playthrough is technically self-contained.

Desktop Dungeons has the player unlocking content through the "campaign", but the missions themselves are short and self-contained.

Escape Goat is a twitch-puzzler with a solid and fair mandatory campaign (short unlockable levels) and a selection of stupidly unfair (but presumably also short) extra levels. Gameplay within each level is independent.

Triple Town is the standalone port of a viral freemium match-3 game.

Tetrobot and Co has short unlockable, otherwise independent levels.

I forgot how Incredipede works, but it's probably short independent unlockables, too.

YOU DA MAN!

Perfect example.

* Unreal Tournament 2004.

* Aliens vs Predator Classic 2000.

Hunie Pop

Kingdom Rush is a good game to play in short sessions ( or sometimes long ones, when you feel like it ). Or how about World of Goo? Also, most Arcade style games, such as various Shoot'em-Ups.

Pushmo depending how good at puzzles you are.

Jones in the Fast Lane. One of my personal favourites in the early 90s. They ported it to flash:
http://home.broadpark.no/~kboye/jones/jones.html

Hotline Miami is the correct choice. But you may not want to stop playing after fifteen minutes.

From this site, looking over my library:

- Where Is My Heart
- Pixeljunk Shooter
- Wacky Wheels
- The Adventures of Shuggy
- Super Puzzle Platformer Deluxe (not sure if you can complete it though, it's more like Tetris)
- Vertical Drop Heroes & Spelunky (depending on your definition of "complete"; you probably won't beat them in that time, but your attempts to do so can be fun too and you will unlock new stuff with them)

Bejeweled 3.

Most rogue-likes are good in short bursts, usually 1-2 dungeons depending on the game. Not so much ToME, but maybe Bionic dues, 15 minutes would be good for 1 dungeon, and maybe 5 minutes extra to manage your inventory. If you are going to be fairly light on it, then casual/easy difficulty keeps it from being too stressful.


Hmmm if you like especially grindy games, 1-2 dungeons in a game like Dark Cloud would be good, since you'll need like 100 hours in order to beat the game, every day or twice a day booting it up and playing a few dungeons would keep it from getting too boring, although optimizing your gear is a bitch if you break anything :(

Hmmm.... Hehe i'll reference a PS1 game from long ago, which is good for kids too. It's... umm... jampop? Oh what was it... *Digs around his archived games* Spin Jam! Great for short bursts and handing it off to kids when you get bored... I think i once got to level 30+... God that was so long ago when we bought it because we were so poor :(