Lego

Thank you! :D

Thank you! It was a long, long... lllong process of procrastinating trial and error=)))

All I can say with certainty is that this is the centerpiece:

Used one of these as the seat piece, with the long end pointed upward. I then reinforced around it with several more brackets focusing on finishing up the enclosure. The entire build's focus was "Technic minifig scale mech suit," so everything was built to prioritise a functional, structurally sound, and aesthetically coherent mech core design. The limbs are just there, pretty much, cheapest and quickest integration builds I could think of.

It uses 100% ball joint for the limbs, the newer Bionicle stuff which is designed for single-plane swivel. The arms are connected to two of these (one on each side):

I placed them vertically and used the lower ball for the arm joint. Initially wanted to use the upper ones as weapon mounts then pauldron mounts, but they're now vestigial.

I then built the "hips" as an extension connected to the seat itself, around one of these:

The arms and legs are pretty basic, it's the design visible in my first post, on top of which I slapped as many angled slates as I could while keeping the armored plating within 2u of thickness overall. Same principle for the pilot enclosure, that one's essentially a bracket-based cockpit (lifting canopy included, that one's two bi-angled brackets on a swivel) and the angled slates are attached directly to that.

It's not a 100% "legal" build, I took advantage of flexibility, used those 3u blue studs to force some angles I couldn't get otherwise, but that's just for aesthetics. The main structure, the skeleton as it were, is 100% legal and as sturdy as I could possibly make it while also keeping it thin. It's a very tight fit for my Technic dude, but eh...

Edit: oh, and the "head" is just decorative, it's a dirty improv I did to cover up the middle plane on top of the canopy/bi-angled brackets. I may work on it some more down the line, give it a proper mount point and some swivel.

Edit 2: tried taking some more detail photos, hopefully they manage to convey the pure improvisation which went into this thing=)) Lotsa' creaking plastic and pinched skin!=)))