About the 20x20 preset
This is a starting point for the custom game builder: a medium 20×20 board carrying 65 mines across 400 cells, or 16.3% density. That puts it in the same difficulty band as Intermediate (40 mines on 16×16), so what changes here is scale rather than difficulty — 335 cells to clear instead of 216.
Tips for This Size
This medium grid balances challenge and play time. Focus on clearing large areas first.