Logic Nine Number Grid

Arrange digits one through nine within a nine by nine matrix. Each horizontal row, vertical column, and three by three quadrant must contain every numeral exactly once.
Four distinct challenge tiers accommodate various skill levels. Higher difficulties present fewer starting clues, demanding deeper analysis. Progress through increasingly complex layouts that reward careful thought and methodical execution.
Tap any vacant square to assign a value. Success relies entirely on logical inference rather than random selection. Complete each board to master the art of numerical placement.