Cursor with Gemini 3. I didn't manually write a single line for it (except for the actual wording). Gemini did the React stuff, styling, writing ffmpeg commands for re-encoding the videos to work better with scroll-based scrubbing, splitting them out into AVIF image sequences for mobile, etc. I use Cursor + Codex for the actual game as well but it involves a lot of manual work - even with a really modular system like Unreal it gets convoluted.

I tried doing a spreadsheet application heavily using Sonnet 4 (https://app.embedsheet.ai/) and found it would make a ton of mistakes and massive files that it would then be unable to reason with, I think if I did it again I'd do all the core stuff by hand.

https://tendayweekcalendar.com/

I did no manual coding except small bug fixing.

They're something like electric vehicles - faster, cheaper, safer, with some new unknowns to be wary of. The bad stuff comes from expecting 2x the work done with half the people. If the employer gives you time to code properly, read, revise, it's all great. You'd be writing code faster, reading more code, understanding more code, having many eyes reviewing the code.

You will get to 10k LOC in a day, which means that you have to set architecture up right away for any new project. You'll need to do best practices, things like XP which people tend to skip over because they don't have time.

It is also very bad with things that it's not trained on, like custom SDKs and integrating GPT-5. This is much like trying to drive your EV through a river.