SHIFT-Space: Toggle edit mode

In Edit Mode

click / drag:       select and move quads/corner points
SHIFT + drag:       move selcted quad/corner point with 10x precision
ALT + drag:         rotate/scale selected quad
Arrow keys:         move selected quad/corner point
SHIFT + Arrow keys: move selected quad/corner point by 10 pixels
ALT + Arrow keys:   rotate/scale selected quad
's':                Solo/unsolo selected quad
'c':                Toggle mouse cursor crosshairs
'r':                Rotate selected layer 90 degrees clock-wise
'h':                Flip selected layer horizontally
'v':                Flip selected layer vertically
'b':                Show/Hide projector bounds