See also: Isometric video game graphics - Wikipedia
Highlights:
- True isometric projection uses a 120° degree angle, and each dimension has the same scale.
- In pixel art it’s more convenient to use a dimetric projection where the angle is \arctan{(\sin30°)} \approx 26.565° and only X and Y dimensions have the same scale. This results in a nice 2:1 pixel ratio for the X and Y lines.