Designing games, especially for mobile devices, requires that developers think through their design of content, both logically and visually. The user interaction tools differs a lot between desktop and mobiles, and does often need to be considered during the development. When the game is also meant to be played through a web browser in some way, advantages and limitations by having that layer, should be taken into account as well, as it restricts access to file system, but at same time provides its own storage functionality. As game development in general is rather complex, this thesis focus is to give an example of a mobile web game, which could be extended and adjusted regarding some specific topics. It also shows that game development frameworks like Phaser, are very useful. The game is developed in Javascript, with the aforementioned Phaser framework. Some results found, shows that Canvas is still superior to WebGL for mobile devices. Atlases do help even for smaller amount of images, although not by very much, and that choosing an appropriate game level generation algorithm as well as its implementation can greatly affect performance, but that there might be trade-off between speed and functionality.