Bipolar
I only made it to the 6th level and didnt get further in 5 tries so the review is based of those levels.
The graphics are simple but effective, except for the smaller icons on the right, some of them i had trouble making out.
The music is soft and relaxing, deeply contrasting the relentless time restriction. Maybe it's the time restriction that's out of place; I don't see the point in having it since later on you're expected to avoid certain combinations, requiring you to plan your moves, and putting a time restriction on that creates a sudden surge in difficulty. The 5 minute limit on every level seems way too arbitrary as well.
But the worst factor for me is not the difficulty or bipolar feel of the game; it's how you're expected to control the flow of the symbols, yet you have no idea what's going to happen when you break a line. I've had too many cases off my row of 4 being introduced to a 5th seed, removing three of them and leaving me with 2 and some useless new symbols. or moving the final symbol into the row of 5 only to have the line next to it collapse, introducing a piece of oil and ruining the whole thing. Difficulty is one thing, but introducing chance and horrible odds is just frustrating.
The issue could be easily solved by letting you see the next 3-5 rows above the playing area before they drop; that way you'll know what's going to happen and can play accordingly.
The controls are a bit wobly as well; i think you would've been better off with a single button toggling horizontal and vertical, although it's a minor issue.
Creatively it's nothing new, maybe except for the introduction of oil symbols, haven't seen that before.
To sum it all up; Calm and tranquil interface suiting the theme of the game (^_^b) accompanied by Random and frustrating gameplay of relentless difficulty (X_Xp)