Thanks for the kind words and the feedback.
As the person who created the puzzles, I totally agree. That last level was shoehorned in last minute to demonstrate how new colours would be unlocked, and to give a sense of how the game progressed even though we essentially ran out of time to implement progression.
We also cut a mechanic (again due to time) which allowed you to upgrade the feedback panel; the idea here was that the messages would become more useful with each upgrade, providing more detail about which colour was involved, where in the grid it was etc.
Thank you for playing and commenting!