Laying out the level
Now, it is time to place the object in the game level so that the game will be fun. Let's make another sprite with dimensions 32 by 32 and give it the color black. We will call this PlaceTurret. It should look something like the following screenshot. You also need to change the origin to the top-left side.
The black areas are going to be the locations where we can place turrets when we click on the screen. This will set up a path for the enemies to follow along. This is where we get into level design. I could write a dozen books on level design, but the three key things to remember are as follows:
The levels should be playable from beginning to end
The levels should have a win/lose condition
The levels should provide at least one thing that is interesting for the player to see, play, or experience
You should make a few different level layouts, and then choose the best one. My level looks like the following screenshot:
