One of my favourite games was Rawbots which was a sandbox simulation game that let you build things with modular parts and program them. I especially liked that the parts were programmable. Most other building games that I know of (TerraTech, Beseige, Robocraft, Reassembly, Captain Forever Remix) don't let you program your creations. What other sandbox simulation games do you know of that let you build and, crucially, program your creations? What games would you recommend to me based on this post?

Starmade has a full logic block and rails system that has seen people make everything from arcade games to a fully transforming modular Voltron. Changes had to be made to the game as people had created clocks linked to jump computers that were too fast for the servers / code to handle. Its still currently free to play (and I suggest reading up on releaeses to get an idea of where you may be comfortable with as development took a nose dive into a poorly planned path a while back).
Shenzhen I/O is on another angle where the game is all about programming - and I believe yet again people have broken the walls and made games within the games.
...AND while ive not bothered with this in game myself, Factorio also involves a lot of programming capability from the trains to circuits, switches and triggers for production.
Maybe not QUITE what you were looking for, but surely of some interest.

Thanks for the recommendations.

I've played Shenzhen I/O before (as well as Zachtronics' other game TIS-100 and Tomorrow Corporation's Human Resource Machine). Tbh, I thought those games were a bit too low level for my tastes (I much preferred using the visual programming UI of Rawbots or the SPRAK language of else Heart.Break(), which allowed you to use higher level abstractions instead bit-twiddling using assembly and a stack) and wasn't too into the game mechanic/goal of having to optimise your programs using as little parts/code/runtime as possible which felt a bit stifling. I like programming games that feel more "sandboxy" and grant you freedom for experimentation without being constrained artificially if that makes sense.

I've had my eyes set on Factorio for a while, but I don't yet have the budget for it. I'm a pretty patient gamer though, so I'm just waiting for it to get really discounted before I get it.

I've not heard of StarMade, which admittedly looks super interesting. Kinda looks MineCraft mixed with No Man's Sky. Shame it isn't on GOG though. I +1'ed the wish for it, which I've linked here, for posterity.

well its still alpha (after ~10 years as its really a side project for the main dev). they plan to open source the code at some point soon, but its def worth a look - especially as you can export .OBJ files and basically utilise it in the manner you would a regular 3D program.

back when the servers were well populated it was a lot of fun (and I dont do MP normally) - especailly with some of the insane contraptions people made. theres a lot of stuff you can download from the community dock to populate your universe though.

personally i still like to dip in to build space stations on SP and hope that development returns to a steady pace.

Sounds great! And it seems like they have Linux support too, so I don't need to use Wine. And you said it's free to play, right? Hmm, I think I might actually give it a go hah.

yes, last i heard it actually ran better on linux, but that may not be the case now (its java based so not sure on all that).

and yes, until it leaves alpha its free to play - best to download direct off the dock. as mentioned before its worth looking through release notes as you can play most if not all version updates (personally i found the end of power 1.0 to be the best overall).

Minecrat has a pretty powerfull programmable block. Maybe not the kind of game you're looking for but it fits your criteria,.
Can be pretty fun, if you're not familiar with the game, have a look at redstone and command block creations...

Frozen Synapse?

the only ones i can think of are puzzlers such as spacechem or opus magnum

It's "action programming" adjacent in that everyone selects their actions/gives orders in advance, then clicks play to play out the turn without interaction, then repeat.

Sure, those have programming gameplay elements, but like you said are more puzzlers (Like Baba Is You or Hack 'n' Slash) where you optimise your solutions than building/sandbox games. That said, some of my favourite games (Bitburner and else Heart.Break()) are also similar in that you have to program solutions to problems in the game, but the languages they use are higher level (JavaScript and SPRAK, respectively, compared to lower level programming like using logic gates to build circuits or using simple assembly-like language and a stack), so it's more convenient to experiment and come up with different solutions which to me makes the games feel more "sandboxy" (I guess Screeps is also similar as that also uses JS, but I haven't tried it).

I think I'm really looking more for games like Dream Car Builder, Stormworks: Build and Rescue, Main Assembly, LogicBots, or even Lego Mindstorms where you actually build robots/vehicles/bases/other "physical" things, then program them to do stuff (though TBH I haven't actually tried any of these, I've only seen gameplay videos about them).

Ah that sounds like Toribash from what I know about it. I think you program the moves of a fighting avatar in it and watch it duke it out with another player's avatar. Or like Mech vs Minions and RoboRally which aren't actually video games, but are board games instead.

yea, i know what you mean, been looking for a arena type of game that implements that specific style of play. One game that came very close is the now almost 13 year old gratuitous space battles. In this game you designed your space ships from a wide variety of hulls and components, gave each of them a specific set of orders and uploaded your fleets either against others or for use against the challenges found inside. Later on a dynamic campaign was added where everyone could upload their fleets too, quite nice

That looks pretty interesting. Reminds me of space battles in Stellaris but 2D like Endless Sky, except you don't control the ships, you just watch the battle play out automatically. You might want to check out Endless Sky. It's seems quite similar to Gratuitous Space Battles and it's free and open-source. It has a lot of very customisable ships so you can build your own space armada, but you have to micro manage the ships instead of programming them before the battles from what I remember of it. It's quite fun, I've sunk many hours playing it.