wow easy to cheat much?
giving this a 3 just cause it's a tower defense game but um yea I his the upgrade button by accident and watched my score go up so I did it again.... and again... and again as you go threw the waves you get more at first you get 50 or what I saw then at wave 5 it goes to 80 and so on with seemingly no limit to how many times you can
It Has Potential
You might also want to introduce a sell feature
...it could become a great tower defence ! It needs graphics, more variety of turrets/monsters/maps, sounds. Also, make harder enemies give more gold instead of always $1. And it takes too long for a monster (after reaching the end of the map) to remove health from you and come back to the map.
There are so many games like this that you should be able to make a great game just by playing one. They have mostly everything it takes to be successful on one of these games. You made all of the weapons balanced, which would be a good thing if the third weapon did not cost significantly more than the first one. also the health does not actually go up as posted.
It's not you,
It's everyone else. So many Tower Defence games, my standards for them are insanely high.