Most gamedev SDKs have a physics engine built into them (e.g. Sprite Kit, Unity and Unreal). But building your own physics engine can be a great way to learn how physics engines work and how you can best exploit them in your own games. Read along and start building your own physics engine.
The A* Algorithm is one of the most popular pathfinding algorithms. The best way to understand it is through some animations and colorful visualizations. Watch this video and you'll have a much better understanding of how and why A* works.
Got a new game idea? Want to test a new game mechanic in an existing game? Learn how to rapidly prototype your gamedev ideas using Sprite Kit in Swift Playgrounds. Very cool.