How to align a border?

Answer 1

A border cannot be aligned, nor sized. A border is positionned on each whole side, and can only define independently width, style and color...
To design border wich doesn't follow this rules, you need to cheat, and handle differents objects to simulate horizontal and vertical rules to be sized/positionned as you want relatively to the concerned box ^^

Example of cheat to define independant shadow to each borders (on ball bouncing):

https://code.sololearn.com/WaGb2G3N4VDR/?ref=app