This game is super addicting! My only complaint - floors 10-60 are in the left column of the level select; leaving floor 70 all by itself in the right column (unless there is a secret second half of the game I'm missing, which would be awesome). This is kind of weird.
My solution for the locking mechanism: pieces have to be next to each other for x seconds (around 5 maybe?) before they lock. This way, you'll still be able to move large blocks as a single unit if they've been in place for awhile, but won't be able to cheat (not quickly, anyway).
In walls down mode, the different building types should have different tile colors, so I can still see what everything is, while enjoying the processing savings of not having to draw all of the buildings.
I don't understand how such a buggy game could get both badges and featured game status. Read the top few dozen comments, and see that this game has had serious bugs from day 1; not major fixes from a programming perspective, but the developers don't seem to have any interest in fixing the things that would greatly improve the user experience.
If there is one thing I really dislike seeing on Kongregate, it's games that are posted and then abandoned. This game has a lot of great features; however it has a few bugs and oversights listed in the comments that shouldn't be too hard to fix. The developer has had several weeks to respond to this feedback, and hasn't even popped his/her head in to say that the problems have been noted and are being worked on. Why would I want to continue playing a game when the EXP system is so broken? And it's not like we're asking you to rewrite the game, just add a few simple fixes to the UI.
The "Spelunker" and "Walled Cave" achievements don't work. I have traversed the entire unfinished dungeon in a single setting (I wasn't sure whether it was get to the 50th floor or get to the 50th floor in one go, so I was thorough). Similarly, I stole 20 walls from a single dungeon, and was not awarded any achievement.
It took me a surprisingly long time to find the shop- this could be pointed out somehow? And some kind of confirmation when things are bought in the shop- not necessarily a yes/no window, but something along the lines of the screen blinking so that I know my click has registered.
A very good start to a game. You need to fix a bug with mining stone after it switches to a separate mining screen, it stops working. Also, I think upgrading the graphics would add a lot of character to the game without too much effort, at this point (you don't seem to have too many).
An interesting game. I have never seen a mechanic like this before, and it is pretty cool. However, this game doesn't have a lot of replay value. You need to add some kind of goals, missions, upgrades, harder difficulties or game modes to unlock, something to "accomplish" in the game.