Two simple demos about Inverse-Kinematics using CCD (cyclic coordinate decent).
It should be pointed out that I use Spherical coordinate system to describe the position of joints (because it is easy to implement lol). Consequently, these projects cannot be used in general.
I may change the two demos into Euler angle representation in my spare time.
Hints: You can use Rodriguez's Rotation Formula to rotate the end bone to the target position:)