Thanks for this. I know I'm personally struggling with this, but this game is INCREDIBLE and it's so high quality in pretty much every aspect.
The bit that didn't click is that overflows don't count. So:
🔴🔵🔴🔴 (1 heart)
Is correctly solved by
⚫🔵🔵⚫
cause the blue is solved, and the second blue doesn't matter because the "1 heart" condition is solved, and technically without a second blue there's no misplacement (e.g. a dot).
The whole time I was trying to find solutions that would only have 1 blue, or 1 red, to match the "1 heart" suggestion, which painted me into an impossible corner for most challenges. there's still bits I don't quite get, but I'm now like... Rank 30? And getting through this!