Let me preface the negative part of this review with some things I enjoyed in your version of Tetris.
- I felt you captured Tetris well; Which most flash versions do not.
- The 'item' system was a great way to make your version unique.
- The horizontal clear item was a great thing to have added on to a Tetris. Can't complain about a five line clear.
- The 'Push Down' item was a fantastic addition. I found it helped immensely.
- The graphics were great; The nuke and hard drop effects were done well.
- The overview of the game once you lost was cool.
Now for the negative, which there's more of, simply because they stand out more.
- There's no soft drop. That really hurts the game.
- You don't get any additional score for hard drops.
- The nuke item makes the game WAY easier than it should be.
- The vertical clear item hurts a lot more than it helps. If you have a bunch of tetris' lined up and then you mess up, have to make a one line clear, and accidentally hit this powerup, boom, you have to use a bunch of line tetriminos so that you can make those tetris'.
- When you pause the game, you can still see the game board. This completely negates the reason for the tetriminos falling.
- When you pause, the items still change.
- If you are a player that uses hard drop a LOT, like I do, then the hard drop sound effect gets extremely annoying, very quickly.
- When you unpause, the music starts over.
- The items changed too rapidly to really be something to aim for. They became more of a 'Well, if I get it, awesome.' thing.
All in all, good game, but it could have been pulled off better. In the future, I'd like to see you make another, improved version, of this idea.