It's an interesting combination of Jenga and Kerplunk - you have balls to throw into the game grid, and by knocking red and blue blocks off the gaming area, you score points. The number of balls are limited, and you have terrain, exploding bombs, and skull blocks getting in your way of trying to score the points you need to clear the grid and move on to the next grid.
Along with the built in levels, there is a level editor for you to build your own challenges, although the N-Gage Arena options only allow you to compare rankings, we can;t see a way to upload and share your levels.
Boom Blox is available through the N-Gage client, as always you will need to go to the showroom section, select Options" and then "Update Now" to see it. Alternatively it's available on the N-Gage website here if you prefer to install games through your computer.