Grid snaps to 10px. Pick a shape or the seat tool, then drag on the chart to draw. Drag the round handle above a selection to rotate (snaps to 15°). Double-click a text box to edit; double-click a seat to clear it. Use the Room presets or drag the right / bottom edges to resize the room. The room layout is shared by every class — switch classes above to re-seat the same desks with a different roster.