So my son & I played this for about 3 hours tonight, or I should say we played 2 hours together as the game requires you to complete a 1 hour "tutorial" that is single player before you can move on.
As the tutorial doles out a few traps & XP, allowing you to upgrade one of your traps, I'm not sure what happens if you skip it (I read somewhere that it is skippable and I'll admit I didn't search long).
They have a stupid timer at the beginning of the round. I say stupid because when you are playing a map for the first time - and some of these are quite large with multiple entrances, you really need more time. I grew very frustrated with this.
There is no "restart" ability. You need to exit, reform the party & restart the level. Very tedious if you're just trying to get another star.
Friend integration into Steam is very weak. To play with others, you are presented with a screen where it's not completely obvious that you have to add a friend - and while it uses Steam names, you HAVE TO TYPE IT IN. Seriously? Why can't they just display my friends list & let me pick? So if you have a friend who has one of those cockeyed names, you get the joy of trying multiple times to get the name right.
Play-wise, it's very similar to Orcs must die but the grind is pretty steep. They have an online store where they let you buy gold and "weekly passes" and skulls for a set amount. I don't mind rewarding them, but I have a feeling the cost for things will increase exponentially at some point. New heroes are 12,000 skulls and I earned about 2,500 in 3 hours of play tonight so you can do the math if you want the other 13 heroes or if you want to spring $29.99 for all 16 heroes at once.
They have increasing rewards for logging in every day - get some free stuff and their specials in the store will change so I bought a new trap tonight (lightning wall trap) because the RNG to get new traps just sucks.
For completing levels and how well you do, you get chests and in my limited play-time, these chests give "common points" on specific traps which you need 100 of these to upgrade from level 1 to level 2 (I'm sure these will increase for each level). I got 1 new trap in the play time we played. You get skulls and XP for each level you complete.
With coop, so far it typically follows a pattern of "enemies out of Rift #1" for 1-2 waves, "enemies out of Rift #2" for the same number of waves and then enemies out of both Rifts simultaneously for 2 or so waves with the last wave having a "boss" that is super tough and will require focus.
Each person gets coins to spend during the round and you need to work together to try & use the highest level traps each person has. Barricades are the most important and having that annoying archer hero helps as he can buy them for 200 less.
We'll be playing it more. The grind isn't bad at the beginning, but we'll see how long this lasts.