Thank you for your feedback!
- Are you referring to endless mode? Based on my tests, the standard (non-endless) mode should be fairly manageable to clear. Hitting a dead end in endless mode is somewhat expected, though it depends on which attempt you get stuck on. AFAIK it should be possible to reach at least around level 30.
- I initially included music during gameplay but felt it might be distracting while players are calculating, so I eventually removed it. Adding a mute button could have been a good middle ground, but this time I opted for a more minimalist approach over convenience (which I seldom do; my previous game took the exact approach of adding a mute button)