I've added some sound effects I found here in itch.io and added them to the first enemy. Only problem is, I implemented it in a general way, so whenever an enemy is hit, the game tries to play that enemy's sound effect. However, I only added a sound effect to the first enemy. Therefore, when you hit another type of enemy, the game tries to play a sound effect which doesn't exist and, since I'm not doing exception handling, the game crashes lol.