Nice little game. Considering it's your first game, congratulations! It's very well done.
Things to consider:
* Difficulty is okay - for the average player, only the later levels (especially the last one) will give some trouble. The rest are either easy, moderate or requires some micromanaging.
* Completionist difficulty is not okay: IT'S ABSURD. I've been playing this for hours and yet I cannot achieve five stars in most levels. The best I can do is 4-stars. The main reason for this is because I exceed the scales spent on upgrades. Since farming scales and spending them on upgrades is the main condition to victory, I believe it is outright impossible to 5-star some of the levels, and extremely difficult to do so on others. This means the "Mastery" medal is extremely hard to achieve and probably one of the hardest medals not only on NG but maybe on all flash gaming communities to be achieved - Even considering the sidequests bonuses.
*Speaking of: There are 2 sidequests that are now permanently locked away because the site they were played on (presumably) is now defunct (also, presumably). They probably awarded nice bonuses which helped completion of the game, and maybe 5-starring some levels.
*Micro Managins pays off: It's the main mechanic of the game that allows for better scores. Since there is limited time and resources, MM makes all the differente. It's possible to beat the game without MM most of the towers, but if you want stars you will need a lot of skill using MM (Portal towers require MM)
*The game provide VERY USEFUL tips that help out on new levels and teach the player the strategy needed to win and possibly to achieve 5 stars on levels, but I still think that it is impossible to do 5-stars on ALL levels.
Overall it's a good game, but maybe not great due to the sheer difficulty in achieving medals now.