Gamers with little time (with train and promotional GA)

They are all good for short sessions, I think. Some of them are better at that than others, though, especially when you're only playing for 30 minutes tops.

Punch Club is a turn-based goofy boxing sim. You can get to a stopping point pretty easily, and there are fast forward functions available in a lot of places so you're not just watching repetitive animations and eating into your time. I think you could manage an in-game day within 30 minutes, maybe even as multiple in-game days. With the way the game works, it's well-suited to just kind of leaving it open between actions while you do other stuff in another window (which definitely accounts for a lot of my play-time).

Spacechem is a tricky one, since it's a really challenging logic puzzle game. If you get the hang of it you can probably solve harder puzzles under 30 minutes, but sometimes it can take trial and error to make it work. It also has fast-forwarding, coincidentally, so you don't have to waste time watching to see what your setup is doing every single time. Though you will need to slow it down for troubleshooting, often enough.

Toribash is basically a fighting game where you take simultaneous turns with your opponent commanding individual muscle groups on a ragdoll. That sounds more complicated than it is, I promise. There is no story at all, you just compete. Matches should not take very long at all, just a few minutes. However, depending on what room you're playing in and how many other players there are you may have to burn a lot of your 30 minutes waiting for your match. Every match is one-on-one with the winner going on to fight whoever has been in the queue the longest, and everyone spectates until it's their turn. I'd say that in a crowded room you could go through the whole process once in 30 minutes, but probably not twice. In a smaller room (or if you just have a winning streak), you could get many matches done in that time.

Aquaria is probably the toughest game to make satisfying progress in within 30 minutes. It's sort of a swimming metroidvania kind of game. You can probably make it to your next checkpoint in that span most of the time, but I'd have some concerns about forgetting what you were doing by the next time you play.

Pirates! Gold is a classic, sort of a sandbox pirate simulator, and can go on as long as you're able to. I've had many sessions where I lost the game in less than 30 minutes. I'm honestly unsure if there's any actual victory condition, I think the game loop just kind of goes on until you fail or get bored of your success and retire (I always failed before anything like that happened, but I had fun doing it). IIRC there are quests that you can do, but I'm not aware of an ending beyond a simple readout of what you accomplished. It would be very, very easy to lose track of time playing it if you're not careful, because of that. But I think that with discipline you could definitely get to a stopping point and quit out within a 30 minute span.

Spelunky is essentially a platformer with roguelike design. It's meant to be played over and over. You will die often, and the levels are procedurally generated so they're different every time. I would honestly be surprised if a single run ever lasted a whole 30 minutes, but then again I've never been very good at it.