I know this game isn't finished, but so far, (no offense) it sucks.
May I suggest changing the sprites?
In the tutorial, you may also want to add what each tower does. It would also be better if you couldn't navigate around small maps. If the sprites, graphics, tutorial, and content are improved, I may change my rate.

It's not bad for a start, but there's an extreme lack of information, I had no idea what the towers did before I read the other reviews, I had no idea what the range of the towers was before I tried them out and I had no idea how they fired.
No clue about enemies either, what will the wave consist of? What do they do? How many are there left?

Some progress bars would be nice too.

Here are my thoughts and suggestions.
1. It works. Things are functional, and that's a good thing.
2. When you put up towers, have grids, so people can better see stuff.
3. I know you said that there isn't sound, and stuff... but keep in mind not making sounds obnoxious or having them interfere with other sounds or music.
4. If you keep up stuff, it should turn out great. This is your first game, so don't make it complicated.

Well it's got potential but it needs a lot of polishing up. Probably shouldnt use sprites for starters. Or if you are you could use some pallette swaps. uhhh what else. Umm yeah try to balance out the towers and that's about it. Keep trying

Fire tower is overpowered . Not Sure if yellow tower does anything.

Game could use Tower Stats (damage,slow) Upgrades music and more .

Too early to upload this .