tetris-time.koenvangilst.nl
After New Year's it can also function as a regular clock:
https://tetris-time.koenvangilst.nl/
For the impatient, it's possible to increase the speed using url parameters:
https://tetris-time.koenvangilst.nl/?to=2025-12-31T23:00:00....
First time I ran it, just off the basic link, it eventually finished with a time of 36:42 (ran at 15:16)
Then I tried turning up the speed and it seemed to make numbers at first but erased its own progress with blank blocks, ending in gibberish.
Maybe another 100 prompts? haha.
The one I shared in the parent is for the New Year's countdown: https://tetris-time.koenvangilst.nl/?mode=countdown&to=2026-...
The basic link should show the current time, even at high speeds: https://tetris-time.koenvangilst.nl/?speed=10
Oh wait, I just tested it on a higher speed (20) and I see what you mean. It's drawing over the existing Tetrominoes! I'm going to max the speed at 10.
What worked particularly well here was a test-driven (TDD) approach. I asked Claude Code to focus only on the algorithm for selecting the next Tetromino (the Tetris blocks), starting with tests. After that, things went smoothly, though it still took many follow-up prompts (around 100) to reach the final result.