To draw a fractal tree, start with a trunk. The trunk should allow 2 branches to grow from its top end. Each following branches should allow for the same, most of the time. Branches closer to the trunk have more chances to grow a single branch, rather than 2. Every time a branch is created, its length should be reduced by a little. As long as a branch is longer than 10 units, it can grow another branch. Every time a branch is created, it should also use a lighter colour. Every time a pair of branches is created, the angle of each branch should be the same, relative to the previous branch.
