I was addicted to this game when I played the online demo. It's really fun, but hard to play unless you follow a particular dungeon building style (i.e. long paths with minimum turns) as the later heroes are insanely hard to kill.
However, this game is extremely short if your good. I bought the game and played it for an hour or so before I got the hang of it. I then beat the game in the same day I bought it. I probably put in 3-5 hours. I can't remember exactly, but there was something like 10 waves of heroes to kill. There was a new Insane Difficulty mode as your reward, but it was too hard.
Basically, you have a large grid of dirt. You have to protect a character called BadMan from heroes who want to capture him. It's like a maze version of capture the flag. You use a chisel to cut out a path for these hero characters to follow and place BadMan as far away from the entrance to your dungeon as you can.
As you chisel the soil, you release these green blobs from the soil you chiseled. They act as your initial defenders and harvesters to make stronger units later. These blobs move around eating soil around them and place nutrients inside the soil. As more nutrients enter the individual soil, you can pop these chunks to release a stronger monster. All the monsters live and die as they fight, grow and eat. Stronger monsters eat weaker monsters. So you have to constantly watch who you create and make sure you have food for that strong monster to eat to survive.
You only have so many chances to chisel the soil. After each wave, the left over number of chisel uses can be used to upgrade all the monsters of a specific type to make them stronger and faster.
The initial wave of enemies consists of one warrior and it jumps up to 2 warriors, a warrior + healer, 2 mages, etc.... The game also gives you about 30 seconds per round to build pathways and create monsters before the new heroes come through.
Basically, you have 1-3 strong heroes to worry about in each wave of attacks. Most characters die in 1-2 attacks from the heroes, so you need a lot of monsters to fight, this is where the game gets addictive.
Overall, on the original mode, if your good you can beat the game in 30 minutes, with slower playthroughs clocking in at about 1-2 hours. This all depends on your dungeon layout. If it has multiple pathways, you can keep the heroes searching everywhere before they even get close to BadMan.
The insane mode was too crazy. The initial wave consists of 3 super heroes that you find near the end of the regular game. You only have 30 seconds to build a super army to beat their insanely high stats and healing abilities This for me was way too hard because I would barely pull out a 1 or 2 of the level 2 or 3 monsters (kinda strong) and they would die in 1 swipe of their sword.... Overall, highly addictive game. Highly replayable if you like the insane mode challenge