If you like this, you might like Dungeon Raid even more. Similar idea: puzzle match, dungeon-crawl theme. But much more addictive, and deeper.
EDIT: fixed the name
EDIT: fixed the name
These games hit a certain sweet spot for me in that you play in short sessions but there's a long term progress you can work towards. That way even when I'm tired on the subway I can chug slowly forward and still feel like I'm making progess. Other times I can rejoice in playing with zenlike brilliance.