I bought Tidalis at the Holiday Sales not because it had a big sale (well, it did get a 50% off), but because I like the developer (Arcen Games) attitude towards charity I wanted to support them. Before trying the game I thought it would be a standard match-4-like game, but with some crazy achievements (64!) that would be impossible to get. I was wrong about both. It is a casual game, but it does require you to be pretty active in the story mode or you'll lose very fast. Especially in the last ~10 levels I had a lot of problem (it doesn't help that they are randomly generated), and I did end up skipping a few to fnish it. Also, the achievements aren't that bad. Most you'll get by just completing story mode, and the rest you'll get by grinding. The worst achievement by far is "To The Moon!" which require your commutative stream lenght to be the distance from the Earth to the Moon. That is a lot of pixels! I had to leave the game running almost 24/7 for three days before that achievement was completed.
I didn't really expect much from Diamond Dan before I started playing, because I didn't really know what it was all about. However, I quickly came to like, and it reminds me of some old-school game that I can't remember the name of. You run around the outside of a temple. Your mission is to get to the bottom while collecting as many treasures as possible and avoiding traps while you progress. It sounds easy, and on easy/medium/hard it's not really that tough. Extreme, however, can be a real challenge in the later levels where there's almost more traps then safe rocks. This is one of those games where you fail a lot, but you keep saying, "One more try. I'll give it just ONE more try, and then I stop!". One day I spent around 4-5 hours on two somewhat simple achievement, which came as a real surprise for me. How easy the various levels are depends a lot on how lucky you are with the generation of the levels. One of the achievements require a speed run on one of the levels, and that really require you to reload that levels a dozen of times before you get the right combination of traps and such to quicky move downwards. Overall the achievements are all doable without too much trouble, and I didn't really find any of them annoying to achievement - not even the 1.000.000 point one (you'll probably have 500k after completing all the others).