Hello Dev! May i ask how the soul's earned mechanics work? Like can you get soul's by killing enemies/bosses or does it increase on how long you've survived in the game?

Hello Mukachiki,
Soul mechanics works in following way: 

Each enemy gives fixed amount of souls according to its type (for example tower = 4)

This will be multiplied by world soul gain coefficient (World 1 = x1, World 8 = x50)

In the end, if you destroy tower in world 8 you will gain 4 x 50 = 200 souls

Thanks now i know how it works :')