An interesting concept, to use your score as a currency. It's a very nice idea, but I found that the projectile being the same color as the player is very distracting, and I would often lose myself amidst all my projectiles and end up dead because of it. Also the projectile precision is very off when moving sideways, or in circles. My projectiles would often be fired to an opposite direction of my cursor, and ESC being the key to open the shop is fine, but on the web browser ESC makes the screen exit fullscreen, so the default key for it should be another one, or have another key binded to it alongside ESC.
But good job nonetheless, hope to see more of your games!