Mechanical geometry
Link lengths, pivot locations and shell shape determine which positions are physically possible. The first task is checking the range of each joint and making sure parts do not collide.
The system
Mechanics and code have to agree.
A robot can only move well when its physical dimensions and its software assumptions match. The design process needs repeated measurement, small tests and careful adjustment.
Servo movement
Servos need calibrated angle limits and a stable power supply. Moving many servos at once can create current spikes, so the power design matters as much as the code.
Inverse kinematics
For a leg, the target foot position can be used to calculate joint angles. This turns a desired position into motor commands, using measured link lengths and a consistent coordinate system.
Movement sequencing
Walking and folding should be treated as sequences of safe poses. A controller can move through those poses gradually instead of commanding every joint to jump immediately.
Test and refine
Test one joint and one leg before combining the whole robot. Record what worked, what jammed, and which angle or timing needs to change.
Current approach
Keep the mechanism understandable, validate one part at a time, and only combine features after the individual movements are reliable.
Every project is also a learning process.
Read about the person building and learning through these projects.