About the 30x30 preset
This is a starting point for the custom game builder: a large 30×30 board carrying 150 mines across 900 cells, or 16.7% 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 — 750 cells to clear instead of 216.
Tips for This Size
Large grids require patience and methodical clearing. Start from multiple points.