3rd Devlog, with an ugly but working menu

In this week, we included new sprites for the player and one enemy. Also we have made a basic but functional main menu and a pause menu. You can pause the game pressing "esc".

The main menu has two options, start and exit. Pls don't press exit button because the demo in the browser will just freeze.

The pause menu has three options, resume, retry and main menu, and they work fine.