This object contains the individual Block objects that form the landscape. It contains just enough Block objects to fill the screen, and as the _terrain object scrolls to the left, the Block objects that leave the screen are moved to the far right side of the _terrain and reused as new Blocks, ensuring continuous scrolling.
The _terrain object also is responsible for collision checks with the _player object, since it has quick access to all information we'll need for collision detection; namely the list of blocks currently on the screen, their size, type, and position. Our main loop then will call on the Terrain object to test for player collision.
Let's work on these main objects, starting with the Player object.