The tutorial shows how to apply a gradient fill to live text in illustrator. You can still edit text after making the gradient fill. Basically, In order to make the gradient, you should add fill color using appearance panel.
This video tutorial demonstrates how to make an orthogonal cube and perspective cube drawings.
This triangle tutorial shows how to draw three different triangle shapes in illustrator
Here you can find out how the “diamond logo”, I designed for a company is drawn. To sum up, the logo design uses a deformed basic pentagonal shape and lines that cut linearly from each other’s corners.