Vertex is another take on the puzzle genre in the G.G. Series and like Energy Chain it's a competent and fairly original concept, but not necessarily an addictive one.
Players move a small glowing green dot at the bottom which is projecting a guide line to the top of the screen. The object is to press buttons to light up the correct number of darkened vertices (remember your geometry?) on the polygons slowly descending towards the "game over line" below your dot. The polygons have numbers in them indicating the number of vertices already illuminated so you just need to do some quick mental arithmetic to calculate the number required to light them all up and make the polygon disappear: touch your chosen mathematical menace with your guide line, then press Y to light one, X for two or A for three vertices. If you go over the number required you'll break your combo and your shot reserve will be reduced by one (though the polygon will still be destroyed). If a polygon touches the line at the bottom you'll lose one of your three "lives." Get the number right and you won't use any of your shot reserve, plus you'll get a chain combo (though you only have a limited amount of time to clear the next if you want to build it up).
You can press B or down on the D-Pad to move the polygons down the screen faster as they normally drop down pretty slowly. After you clear enough to fill the appropriate gauge the level will increase, but this doesn't increase the speed of decent; instead you'll find the complexity of the polygons will increase. In the beginning you'll largely be facing a series of squares with the odd pentagon thrown in, but eventually the number of pentagons increases and then hexagons appear (presumably more complex polygons will be seen in higher levels); frequently requiring multiple button presses to clear each one. The real challenge comes from the special waves that happen between levels where you're required to eliminate all polygons; now appearing in larger groups and descending at a greater rate of speed.
As with other G.G. Series titles the top screen will record some stats to give you a goal to shoot for, in this case your high score, your highest level reached and biggest chain. Vertex is a good addition to the vast DSiWare puzzle library and hopefully it will get a more global release along with the rest of the G.G. Series.