When making games you need to worry about many different things which can make it look intimidating at first:
- Game development: programming the game logic.
- Game assets: images, artwork, sound, animations.
- Game content: levels, story.
There is an easy way to take one of the three out of the equation for when you are just starting, which is to use plain rectangles as artwork. In this manner, you can work on the game mechanics right away, without having to spend money or time in making the artwork. Moreover, using rectangles at first gives you a better idea of your artwork requirements.
Using rectangles is s quick way to focus on the game itself and post-pone the game asset creation process for when things are more clear.
The following video is part of The Complete Mobile Game Development Course – Build 15 Games and shows an example of using this methodology.
I always did this in an intuitive way, but I saw it for the first time explained (along with many other great tips to get started) in this amazing article by Christer Kaitila.