We all know that collision detection is imperative to any game. Regardless of whether it's a hockey game, or Call of Angry eight year olds, the game needs to detect collisions of hockey pucks, bullets, swords, feet on the ground—you name it and there are a ton of collisions that need to be detected. For our game, we are only going to detect simple boxes colliding with each other between the player and enemies, the platforms, and the bullets colliding with enemies.
We are going to make things super easy; first we are going to detect the player's bounding box.
Note
What's a bounding box? Simple! Think of when you're creating your sprites; there's a box surrounding your image? You could think of a collision bounding box like that, the small box that your sprite fits in or within a defined space. You can (and we will) adjust the size of the bounding box to fit the sprite; you can have it larger or smaller depending on your needs.
With that all explained, let's hop into our Player...