TL;DR- About 90% of the positive reviews are from people that stopped playing before act 2 is completed, so their opinions are about the part of the game that works properly and is fun. But that leaves out 1/3rd of the entire game, which is the exact opposite. The game is hard/fun for the first 2/3rds, and completely annoying, unbalanced, unfun, and unfair for the final 1/3rd. I guess most players lose interest in this game in about 10 hours or less, which should already tell you something is wrong since tower defense games tend to garner hundreds of hours of playtime for hardcore players when done well (Defense Grid and Dungeon Warfare games, for example).
So, this is a game very similar to Dungeon Warfare. In fact it even uses some of the EXACT same traps even using the same icons for them. Some people say this game is better than Dungeon Warfare 1 or 2, but those people are flat-out wrong. The levels in this game come in 3 acts. The first 2 acts are pretty fun, but there are a few badly designed/badly balanced maps that are difficult for all the wrong reasons. Also ghosts are a very very annoying unbalanced enemy with no counter available to you at all. You have to build your entire strategy around ghosts every time they are in a level, and even then it's often not enough (especially on hard mode/endless).
Act 3 is where this game falls to pieces completely. The vast majority of maps are so unbalanced there's no point even playing act 3. You have less than half the money you need, there are often so many gaps you need to fill to create a decent monster path that you run out of all your starting money just trying to create a path (and that's with every single thing in the game unlocked including ways to lower costs)--and by the way, the path is still not complete when you run out of money. So there's no money left for traps.
The ghost enemies have no real counter, even with upgraded lanterns and planning your entire map around killing ghosts, often several of them will get through your traps because they are overpowered. They go invisible and can't be damaged, so you need insanely long trap mazes to kill a single ghost. In act 3, it's not uncommon to have 6+ ghosts all coming at the same time just waltzing through your traps taking little to no damage. What can you do about it? Nothing. There isn't a single trap in the game designed to give you damage on ghosts. Good game design dictates that for every problem there should be at least one solution. The provided solution is a trap that does no damage, but when upgraded makes the ghost visible slightly more often than before, but it has a very small range. It works well enough for act 1, barely works by the end of act 2, and completely fails by act 3. There should be a weapon that targets ghost directly, and the fact that there isn't means that the dev is so worried about making the game too easy that they decided to make it impossible instead.
Of course, at this point ghosts aren't even the worst blunder from a game design perspective. Now there are also teleporting enemies. They just disappear, go past all your defenses and go straight to the crystal you're trying to protect and there's no counter to them. Even if you try to build your entire strategy around them, it won't work. In act 3, there aren't many walls around the area where the crystal is, so since most of the traps in the game have to be installed in a wall, you can't do anything to defend the area. Did I mention that both ghosts and teleporters are immune to floor-based traps? So they can't be damaged at all by floor-based traps, wink out of existence at least half the time, and can bypass all your defenses until they hit an area where you can only build floor traps because there aren't any walls for placing wall traps, which would be insufficient anyway because you'd have to be able to rapidly 1-shot 4-5 of them at a time, and nothing in this game can even 1-shot a single enemy, let alone multiple enemies rapidly.
I have to assume the dev got sick of making the game around the end of act 2 because the quality falls off a cliff and it CLEARLY wasn't tested properly. The balance in this game is towards the difficult side for tower defense games, which is generally what I prefer, but it goes from hard to impossible towards the end of act 2 and there are levels where I seriously don't believe the dev could beat them on hard difficulty. I don't even believe the dev played the levels a single time. That's how badly they are made.
The positive reviews for this game come mostly from 2 experiences: 1) people who played a couple hours and never came back, and 2) People that played on easy/medium difficulty (and most of them didn't complete the game either). If you actually play this on hard and try to complete the game, you'll just want to give up after a while because the fun just evaporates as soon as it becomes apparent that the new enemy types have no counter. You are not given enough to work with and thus in act 3 on most levels you'll be massively underfunded, underpowered, and completely incapable of coming up with a strategy that will keep teleporters, ghosts, and spawners from just walking through your trap maze as if it wasn't there.
This game could be fixed, but I think by now it would've been if the dev cared. There's been plenty of time to fix these glaring design flaws by simply introducing something to counter ghosts directly (a trap that damages them while invisible), a counter to teleporting (a trap that does damage, not some bs like the lantern) or honestly just removing those badly designed enemies instead, reworking most of the level designs in act 3, and adding some form of boost to the economy or making crates free for the first 10 or so instead of a handful. If every level requires you to start off by spending all of your gold making a partial path with crates, then it wasn't designed properly. The way the traps in this game work, you can't just build freestanding traps so you need to keep enemies in walled areas. But you can't because the entire goal of act 3 is to take away all of the tools you have, which were barely sufficient in act 2.
This game could have been a fun little knock-off of the better Dungeon Warfare games, but instead it's a game that is increasingly unfair to the player until the player stops playing.
