Creating a floor in the GameScene

GameScene.swift

import SpriteKit

class GameScene: SKScene {
    let floor = SKSpriteNode(imageNamed: "blue")
    
    override func didMoveToView(view: SKView) {
        setupFloor()
    }
    
    func setupFloor() {
        // we define a name to our node
        floor.name = "floor"
        
        // the size is represented by the CGSize
        // note that we are getting the size (CGSize) from the scene
        // and it will fill 1/3 of the screen
        floor.size = CGSize(width: self.size.width * 3, height: self.size.height/3)
        
        // we are putting the floor in the base of our screen
        floor.position = CGPoint(x: CGRectGetMinX(self.frame) + (floor.size.width / 2),
            y: CGRectGetMinY(self.frame) + (floor.size.height/2))
        
        // this add the floor to the scene in order to appear in the screen
        addChild(floor)
    }
}