Software engineer. These are the things I build when I'm not writing software - one project per daughter so far, each starting from a blank Fusion 360 sketch and ending as an object that works.
Each one meant learning a discipline I didn't have: mechanism design, electronics, industrial design, and the very long iteration loop that comes with physical parts. The write-ups are detailed because the finished object is the least interesting part of it.
A wearable, battery-powered triceratops that clips into hair. Press the eye and it lights up, opens its jaw, swings its tail, and roars.
Everything in it derives from one constraint - it has to be comfortable on a nine-year-old's head all day. That forced a thin body, which forced a worm gear to lay the motor flat, which collapsed the whole drivetrain into one plane. The linkage was sized symbolically in SymPy rather than by printing three versions of it.
Fusion 360 · ATmega32U4 · worm-gear drivetrain · SymPy · PLA
A two-part wireless "ask and answer" device. Press a chore on the remote, a sign lights up across the room and speaks it, and she answers yes or no with a button on top.
It started on WiFi and I abandoned it - association from a cold wake was too slow and, worse, unpredictable. ESP-NOW removed the network entirely, which is what made it possible to tear the radio down between presses and sleep the remote on a battery.
Fusion 360 · ESP32 · ESP-NOW · Arduino/C++ · 3D printing