Glitchy Defender is more like it
Your programming skills need serious work. Some of the bugs and glitches I'm going to outline may or may not be my fault, but there are a few that definitely calls for blueprint recalling. Anyways...
--I've ended up have 0 money by the time I reached the volcano levels (I wiped out the first wave with spells only lol).
--The money counter at Ultimate Slots doesn't support 5 digit numbers.
--I was able to dig in between waves. This might have something to do with me still having the shovel selected while completing a level.
--If you're in the process of digging, you can hit the pause button and finish digging. If you had the mind to, you could dig out entire maps by abusing this oversight.
--I ended up having 23 credits for Ultimate Slots in some levels. I'm very sure I didn't dig out this much treasure. And no, that wasn't from dig/pausing. I don't have THAT much patience.
--If you place units across from each other, both will get experience, resulting in double exp (from the monster, not for each defender) and absurdly rapid leveling. Especially true of Ninjas and Dragons. This doesn't make sense.
Glitches aside though, the graphics and sounds are very high quality. The concept isn't as great however, although having defenders at corners rotating once to finish off the boss-like monsters is interesting. And the game seemed a bit cheesy and pointless in terms of story, considering you threw a last bit after you finish the game.
You put a nice curveball in the game by introducing digging for treasure. Go for as many potions as you can, or should you worry about the monsters reaching the end? I find it a bit strange how treasure chests don't give you money, but meh. Oh, and some of the tiles are pretty hard to select, notably the ones behind raised terrain or other obstructions, such as Dragons.
The spell system is also interesting, in that you can assist your defenders. Unfortunately when you see the whole picture, it's basically more MP cost, more damage, better spells. I personally never resorted to more than poison and lightning.
Some finer points:
--Knights and Warriors are pretty useless. Their purpose is to slaughter units at the edge of the path. You can deal just as much damage or more by placing a cheaper ranged unit at the outside edge of a corner, since the monsters will traverse both squares of the Archer or Mage's range, three for the Ninja, and an awesome four for the Dragon.
--Oh, and Dragons make everything else obsolete, assuming you can afford them.
--Placing defenders further along the path allow you more digging time. More digging time = more mana potions = more spells you can chuck at them.
--Ultimate Slots can probably be viewed as mostly an annoyance since you're pretty much not going to win much, and if you do, the denominations are going to be 100, 250, 300, or 500. That's pretty weak, unless you win the 500 prize early and often. Also, clearing terrain just so you can dig is not worthwhile, unless you're desperate for mana potions for some reason.
--I like how the speed of the monster played a role into how much damage it would take from defenders.
--Level 2 defenders easily became level 3 defenders. The amount of exp needed to level again should change, not stay at the static 1500.
Personally I was able to get a score over 100,000, pool up $15,000 after the end game (which I beat with two Dragons) and stashed away 26 mana potions. Sure, the game it hard if you're just getting adjusted to it, but giving it some thought, you can definitely make this a joke. You can't really just expect to get away with afking (like in Defend Your Castle) most of the time and be flawless, but just a little nudge with a spell or two and you're pretty much good to go, assuming you didn't come off with a bad start in the earlier levels.