Drop7 is a game that’s a little like what would happen if you crossed Tetris and Sodoku, and I have been playing it a lot recently!

I discovered a flash version of the game first, named Chain Factor and got a bit addicted to it so I went looking for a version I could play on my iPod Touch and iPad. Drop7 is what I found, and I’m really enjoying it.

In this game, you drop single blocks one by one into a grid of seven by seven blocks. Unlike Tetris-like games, you have an unlimited amount of time to choose where to drop each block, and they’re dropped simply by touching the column you want to drop the block into.

Each block has a digit 1-7 written on it, and if the digit on a block matches the number of adjacent blocks in its row or column, any blocks with that digit on them will explode and the blocks above it will “fall” to fill in the gaps. So if you drop three blocks so they’re all touching in a row, and one or more of those blocks has the digit “3″ on it, the blocks with the “3″ will explode, and so on. You score points for every block which explodes.

If the blocks dropping to fill the gaps after an explosion creates another valid move, the explosions repeat – this is called a chain. Scores for blocks exploding in a chain are much higher than scores for blocks that explode all at the same time:

• Initial round of blocks: 7 points per block.
• Second step of a chain: 39 points per block.
• Third step of a chain: 109 points per block.

I can’t tell you the values after that, but they keep increasing rapidly. I once (accidentally, I must admit) created a chain that was eleven moves long and scored a phenomenal amount of points with it. Setting up chains that will explode one by one like dominoes is a challenge made harder by the fact that some blocks initially have “hidden” values and will only reveal their digits after two adjacent blocks have exploded to “break them open”. After a certain number of blocks are dropped, you move up a level which introduces a row of hidden blocks at the bottom of the screen.

It’s a difficult game to describe because it doesn’t sound interesting but it’s really both interesting and one of those games that stays interesting the longer you play. I also really like that there’s an unlimited amount of time to drop each block because I really hate games that just get faster and faster until my fingers can’t keep up! I was skeptical at first because at US$2.99 it’s more than most simple games I buy, but it’s definitely been worth the price. Drop7 is a universal app which works on iPad, iPhone and iPod Touch.

I highly recommend Drop7 to anybody who likes number or shape based logic games.

- Ricky