Good job for making a TD game that kept me from getting bored. One thing I noticed is that barracks are largely unneeded. I usually just had one at the very end of the road that might have seen some action once or twice per level. There just seem to be too many counters to barracks such that a mage or archer tower is always more useful. Part of this might be the reinforce spell being too strong. Maybe 3 reinforcements every 20 or 25 seconds would be a better balance than 2 per 10. Also, because of upgrade restrictions, the early challenges end up being harder than the later ones. I had a horrible time on level 3, but one shot all of the ones past the first boss (save for the one where you only have barracks and artillery and there are flying enemies...took me a bit too long to puzzle that one out).
There needs to be some limit on reactors or perhaps a stacking cost similar to the tech domes, because right now there's nothing stopping me from spamming reactors and then spamming guns to win easily.
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