Bloodtide Tower Defense

PREPARE YOUR DEFENSES
We've time-traveled from the far future to conquer these lands. But an ancient blood cult from a time even more distant past has also time-traveled here to take it for their own. Prepare your defenses accordingly.
BEWARE THE BLOOD CULT
Seven types of enemy cultists, each with strengths and weaknesses, are intending to break your defenses. We obviously have to kill them to succeed, but beware: from where their blood spills, other cultists gain power. Felled a Sprinter? His blood will speed others up. Toppled a Healer? His blood regenerates the health of the still-living. Killed one of the guys in armor? His blood is empowered to increases the defenses of his comrades. That, or they just picked up one of the pieces of armor from his corpse... we really can't tell the difference. Adapt your strategy accordingly. 
EMPOWER YOUR TOWERS
Earn and spend skill points to improve tower performance. From basic improvements like increased damage or range, or more sophisticated improvements such as flinging a cultist even further into the past, skill points can take a tower from mundane to overpowered.
Explore tower variants, changing the behavior of tower itself. Perhaps you want your poison tower to put down poisonous gas clouds instead of shooting poisonous darts? They are both viable strategies. Perhaps you want your machine gun tower to shoot at entire areas? It's an option too. 
Skill improvements and variants are available across all seven tower types. 
CONTROL THE BATTLEFIELD
Conquer 30 handcrafted stages, with specially designed enemy waves. Adjust difficulty as you see fit. Or, keep the challenge fresh by enabling the wave randomizer, to further test and temper your strategy. 
TUTORIALS AND REFERENCE GUIDES
And these helpers might even contain some lore! But who cares about the lore; this is a tower defense game. 
EVERYTHING MADE BY HUMANS
Just two humans, actually. The one who made the art, and the one who made the everything else.