The number that stuck out was 200K lines of code. Can you expand on why so much code had to be written and which parts were the longest (time and/or code) and hardest bits?
The firmware is about 110K lines: MIDI recording + streaming, USB, Bluetooth, Wi-Fi, web APIs, storage, OTA updates, diagnostics, security, peripherals, provisioning, and an embedded web interface.
There’s a lot required to make a full-featured product.
I suspect that 110k number might include the ESP-IDF libraries as well as his own code.
I've written a fairly feature-complete handheld device based on the esp32-s2 and the codebase is about 9k sloc of the C I've written, but that number explodes to almost 40k sloc if I include the esp-idf's imported libraries.
Nearly every component gets tested: sdcard, clock, battery, anti-counterfeit IC, led, buzzer, the tactile-switch!