This video is also part of the course called “Basic Movements.”
While many tai chi classes focus almost entirely on the learning of a form/routine, most teachers will at least incorporate some sort of warmup routine that involve basic stretches, stances, and loosening of the joints.
Traditional classes will often spend some time on standard martial art exercises like stance training, hand shapes, footwork patterns, arm positions, hip rotations, waist movements, spine movements, kicks, and concentration drills.
Some of these basic exercises are combined with internal skills, visualizing, breathing exercises, and energy cultivation.
This video is more than 12 minutes long. However, when I do the warmups myself, as part of a longer workout, I do them all in a minute or two.