Well, I personnaly prefer an original concept made by the author than a copy of something, evn if it's your first. You watch the tutorial. I did it to, so I can see some differences, you tweeked some stuff. I like the fact that the center has health now. However, I think you could polish it more, work on the balance of difficulty, make it start a bit quicker too, and make a real difference between waves. You could also make it unique by changing the assets.
Well done :)