Delightful! Answers to some questions:
- Moving off-beat is not explicitly punished, but if you get too far off the rhythm the game advances whether you're ready or not. So the main danger is that enemies get a free hit. The timing is actually quite generous, meant to help the game work properly on emulators and televisions with a lot of display lag
- The compo version ends after stage 1-4, so you were pretty close to completing the demo content. I wanted it to end with a proper boss fight, but ran out of time to implement it
- You guessed correctly: gameplay is heavily inspired by Crypt of the Necrodancer and Cadence of Hyrule. The NES isn't fast enough to process the updates in the same way as those games, so Tactus will necessarily diverge in terms of behavior, and that's fine
- The final version is planned to have much more content, especially music tracks. Many of the current limitations were due to the time and space constraints for the compo