I have played a fair share of Tetris in my day. In the arcade, on the original spinach-green Game Boy, 3D Tetris, every Tetris variation you can name. I mention this because Akihabara - Feel the Rhythm describes itself as Match 4, but it's more like a hybrid between Match 4 and Tetris. Except where it isn't, which is everywhere that matters.
I'm going to assume you have played Tetris, or at least seen someone play Tetris. Different shaped pieces fall one at a time from the top of the screen to the bottom of the screen. You want to arrange the shapes to make lines, which removes the line from the board. If any part of the board fills enough to go past the top of the screen, you lose.
Before we talk about the differences, let's talk about how Akihabara - Feel the Rhythm is similar to Tetris. Different shaped pieces fall from the top of a 4x8 grid to the bottom. You want to match up the shapes to remove them from the board. The game ends if any part of the board gets filled.
In Tetris, shapes fall one at a time and can be moved horizontally around the board, or rotated, to arrange them in a suitable pattern for making lines. In Akihabara - Feel the Rhythm, shapes fall 4 at a time in a horizontal line. You cannot move or rotate the shapes. Instead, you are allowed to replace one shape at a time that is currently falling with an arbitrary shape. Once a shape hits the bottom of the screen, or another shape, it's locked in and cannot be changed. You change shapes by clicking the mouse as a vertical line moves over them, the line moving from left to right across the screen at a speed determined by the tempo of the music.
In Tetris, you know what the next shape is going to beforehand. This allows you to strategize and think ahead. In Akihabara - Feel the Rhythm, you do not know what the next shape will be, so your decisions are entirely reactionary.
In Tetris, the game doesn't end until a shape extends past the top of the board. This means that if one part of the board is getting close to the top, you can move shapes to another part to buy yourself some time. In Akihabara - Feel the Rhythm, a horizontal line of shapes covering the length of the board falls at the same time. Thus every column will increase in height by one with each new row of shapes, no matter what you do. Even if the rest of the board is empty, if a single column is at the top, you are guaranteed to lose, and cannot do anything to stop it.
There are additional game mechanics — score modifiers, special shapes that remove all nearby shapes, etc. None of them change the fact that the game just isn't very well designed, and isn't fun to play. Akihabara - Feel the Rhythm is an excercise in frustration rather than relaxation. You have so little control over the game; you cannot move shapes, you can only change shapes to what the game says you can change them to, you can only change the shapes if the vertical line happens to be over them at that second, and only while they are falling. The closer you get to the top of the board, the more impossible it becomes to change shapes in time.
You do not know what the next shape is, so you are purely guessing what shapes you should change now. Even when you make decisions that seem rational based on the available information, the lack of information and control over the board means you will often fail. Tetris is a game of planning and skill, but this is a game of luck and reaction speeds.
I honestly cannot recommend this game to anyone. From a fundamental design perspective, it's just broken.
