The idea is good, but I've got some suggestions, I also noticed some bugs.
At first the bugs:
1. Once after entering the tutorial after being killed I entered the summary screen with the info about the waves survived etc.
2. Then when I tried to enter the game I was playing with no forest but with the tutorial screen in the background;
3. At this time when clicking on the game buttons I was also firing arrows
4. and suddenly the man that I control dissappeared and the game got stucked with no enemies and no archer.
Suggestions:
1. Make the archer able to move left/right;
2. Balance the power of arrows in the beginning and the speed of the enemies, because it is impossible to kill most of the enemies and especially the boss;
3. I assume that possibilities of doing upgrades will be added later?
4. As already if you hold the left mouse button you keep firing, maybe considering an autofire mode?
It is a good base for further development :-)