Different Slants on Simple Geometric Figures
If you change the viewing angle of a circle, a square, or an equilateral triangle, you can create several different interesting figures.
Snapshots 1-3: circle, ellipse, straight line
Snapshots 4-6: rectangle, parallelogram, rhombus
Snapshots 7-9: acute triangle, obtuse triangle, right triangle
It is also possible, by the reverse procedure, to start with an ellipse and turn it into a circle; to start with a rectangle, parallelogram, or rhombus and turn it into a square; to turn any of the triangles into an equilateral triangle.