TerraTech

Terratech is a surprising game. Seemingly simplistic and unambitious, but the reality is that it's the exact opposite of "ocean wide and an inch deep". Terratech's maybe a few inches wide, but there's definitely at least a mile of depth here.
In terms of only an inch wide, the building mechanics are extremely intuitive and easy to grasp, just grab a block with your cursor and connect to a different block via their attachment points. Only some basic physics are simulated like mass, gravity, inertia, but it fits the game very well and allows things to remain intuitive. The campaign and NPCs are no doubt too simplified, and I wouldn't mind a more difficult and varied challenge and a reason to build and experiment, but these are secondary in this game and serve only as a unlock/progression conduit.
On the other, mile deep hand, the number of different shapes and functions of the blocks makes it so fun and engaging. From getting your first Frankenstein's monster by adding bits of your defeated foes to your own vehicle and letting it grow to a chaotic, unsightly mountain of a monstrosity. Unbalanced, moving on an ill fitting set of wheels and tracks of various sizes and purposes, bristling with random selection of weaponry, everything scavenged from the burning wrecks of your enemies. To your elegant and deadly, streamlined to perfection, pre-planned and carefully crafted, heavily armoured and armed flagship that is maybe a tank, a mining and refining complex, a flying fortress, or maybe all 3 at once. A behemoth that can obliterate any size target from beyond the horizon in a matter of seconds. And everything between these two extremes.
The building mechanics are vastly improved from the time I first played it many, many years ago. Back then, even building a simple mining, refining, selling structure was a major pain steeped in tedium and frustration. There is rarely any need to alt-tab to check wiki or forums about something specific. Building still could use many improvements though, like drag building conveyor belts, mirror building, exploded view for inspection of deep internals in large builds, modular building - now you can only place blocks one by one (patch 1.5.3 from a month ago introduced a new connecting block that allows modularity though).
Where the game falls short is the counterpart to its extremely fun building loop, the world where your creations live. There just isn't anywhere near enough challenges and reasons to build and experiment with different types of crafts and structures. The terrain, despite having fairly varied biomes, only ranges from very flat to slightly bumpy, even in the "mountains". The biomes areas are very small and scattered around in random patches. The world doesn't change as you travel, you just go, very quickly, through the same bits of grassland, desert, salt flats, hills etc. There's almost never any necessity to purpose build something to allow progression, the entire world just blends into colourful patchwork. I would love it if the biomes were much larger, both horizontally and vertically so that making a helicopter to get to the top of the mountains, or a speeder to get through the salt flats would make sense.
I've had some of the most fun during the Slippery Slope challenge, where you have to build a very specific vehicle and have restricted blocks. After an hour of failing I managed it with a tiny car utilizing a weapon with extreme recoil, mounted backwards to help me move through the obstacle course. I just wish there were more reasons to build something specific as now it boils down to making several blueprints for vehicles - regular tank, hover tank, fast tank, flying tank, and structures - defence turret, charging station, autominer template, refining and selling template. I still had plenty of fun doing those, but the game has so much unrealised potential that it leaves me wanting more.
Having said all that, not only the devs are still adding new qos features and blocks to Terratech, but they have a new game - Terratech Worlds in development, which seems to be addressing the majority, if not all of my wishlist for this game. I can't wait for that to release.
In the meantime, I'd absolutely recommend Terratech even at full price.

Yeah its pretty fun. but there's only one playstyle. i wish there was more options regarding being able to turn down the obnoxious enemy aggro and spawns, i tried to do a harvesting peaceful run, but no, enemies every 10 meters, and the ONLY way to deal with them is blow them up, so why have the entire crafting harvesting aspect if you harvesting craft needs to be shielded and armed to the teeth just to stand a chance of getting back to base with enough resources to cover what you lost getting them.

TLDR, add settings to customise enemy spawning and AI

OVERALL FUN. Kill the hostiles, scavage the remains, make yourself bigger, faster, stronger and better. dont worry, they die slowly for your satisfaction. no blood, no gore. just tech on tech slaughterfests. the evolution from small and scared to big bad boss guy is slow and annoying, but very much worth it...and so very satisfying

TerraTech!
This is a cute little game made for people who really like building LEGO. Since that's basically how it works. You snap pieces together into whatever you can think of. Like hovering tanks with jets. Or goofy-looking cars with auto-targeting missiles. Or a massive tank-treaded behemoth with an ungodly amount of firepower, casting a mile-long shadow over once-peaceful grassy plains.
You start as a scrawny cart with maybe one or two guns, beating up enemy Techs your size and hastily taking their lunch money.
As you destroy more rival Techs, you'll collect the blocks they drop, using them to augment yourself into a perfect killing machine. Missions and building factories will also net you some cool stuff.
Alternatively you can play in creative mode/the R&D Labs DLC, which are both fun experiences that give you the chance to build anything you want.
The game has modding support, ranging from skins to brand-new blocks, weapons, and even more game-changing stuff! (Note: for some mods, you'll need to install an external modloader, but it's a very quick process.)
And, the best part?
From today to February 18th, it's only $4.99/$6.39 with the R&D labs DLC, on sale!
I would definitely recommend buying TerraTech if you or a relative love building games/LEGO. Since there's online co-op, too!

This completely satisfies the desire for factory organization and hack-n-slash battles. What a niche, what an art!

A great game with dedicated devs. When I got it I didn't think the game would still recieve updates. Rarely found bugs in game and when I did, they were only minor. I also found one of my creations that I posted on workshop in a multiplayer server, so fun. Highly recommend.

super fun a very small amount of jank and after 200 hours i got board but still i got it on sale and 200 hours of fun very worth the only recommendation I have is to get voice actors because I don't like reading but its really not that bad