Tidalis is a decent little puzzler that could have done with touch controls or a 3DS version - in fact, if you told me that this was a former mobile phone game, I wouldn't doubt you for a second. you see, the object of the game is to chain together blocks by directing a stream of energy through them, but the energy will only move in the direction painted on each block. You can change the directions on each arrowed block, allowing you to set up chains that weren't there before. It gets more complicated from there, with special blocks that stop streams in their tracks, others that need to be smashed on the bottom of the playfield, and others besides.
To be honest, I've found the default difficulty rather easy and relaxing, which is how a casual puzzle game should be IMO - a casual puzzler should never frustrate the player with arbitrary difficulty spikes, it should be the mental equivalent to a light morning jog - only enough exercise to get the blood pumping, and the brain slightly warm. In what I've played of Tidalis, the only place I was continually having difficulty was the "get 7500 pints in 4 minutes" stage, and that's purely because it was pure RNG luck-based ♥♥♥♥♥♥oel.
That's the main criticism I have of the game - there's an element of randomness that's slightly unwelcome in a casual environment, though not the same sort that plagues "pay-to-win" crap like Candy Crush Saga, thank goodness. The other gripe I have with the game is the bizarre cutscenes, which are needlessly distracting and try-hard unfunny to boot. but I don't want to sound too harsh on the game - it's a great little time-waster, especially for 79p during a Steam Sale, or as part of an indie bundle (or for free from a Steam friend, thanks Broodje Gezond!). There's some nice, folksy piano/flute-led music there, too, if you're into that kind of thing.
Overall, yeah, I'd recommend it - if you can get it for cheap or free. It's not really worth £4.