Frontier Flags

Chord a revealed number when surrounding flags match its count to open remaining neighbors together. Incorrect flags can still expose a mine; loss reveals the mine positions for review.

Use revealed neighbor counts to find all safe squares. Opening a mine ends the expedition; flagging is optional.

Tap or click the controls. Keyboard: Tab and Enter/Space operate every button; arrows/WASD move where available, R restarts, Z undoes calm puzzles.

This challenge has reachable failure. Restart returns to the same fair opening.