Use the sliders to adjust the matrix. The values are very sensitive, however (don't go greater than 2). I don't know how to change that. If you want to reset back to the initial state (the identity matrix), press "R".
Just wanted to test my linear algebra skills. The vertices on the triangle are transformed by the matrix represented by the variables. You can scale, skew, and translate the triangle. The z-axis does nothing at the moment since I don't have a view matrix, so it is essentially a 2D transformation at the moment. If you don't know linear algebra the math may seem overwhelming. This is college-level math, so I don't blame you. Anybody who does know linear algebra, however; the transformation matrix is a 4x4 matrix. I didn't include the 4th row in the representation because in graphics we don't use it. "w" stays at one, it's a trick to let us represent translations inside a matrix, which normally you can't do in a transformation. Which is still correct; technically we are skewing in the 4th dimension and casting a shadow back into the 3rd dimension, it just looks like a transformation in 3d space (and 2d space, of course). My mind was blown when I found that out.
