text rotation is sucky.

box.go

@@ -219,3 +219,17 @@ func (b Box) OuterConstrain(bounds, other Box) Box {
 	}
 	return newBox
 }
+
+// Rotate rotates a box's corners by a given radian rotation angle.
+func (b Box) Rotate(radians float64) Box {
+	cx, cy := b.Center()
+
+	ltx, lty := Math.RotateCoordinate(cx, cy, b.Left, b.Top, radians)
+	rbx, rby := Math.RotateCoordinate(cx, cy, b.Right, b.Bottom, radians)
+	return Box{
+		Top:    lty,
+		Left:   ltx,
+		Right:  rbx,
+		Bottom: rby,
+	}
+}