My first impressions were that the graphics were brilliant and the effects look really good. The music also enhances the game nicely. It was also very easy to pick up and play for a few minutes at a time. However, with only 9 levels, it's all over very quickly - I felt I had gotten everything I could from the game after a couple of hours, and the other difficulty settings were too hard for me. The extra challenges didn't add anything, as they basically just ask you to do levels again but without losing any lives, or getting a set score. If there were maybe twice as many levels, and an actual story, this game would be a must-have. As it is, it's probably worth it if you have the persistance to finish the harder difficulties.
When I first came across Nanostray on the DS it reminded me of games I used to love playing on my SNES, which were Super Aleste and Axelay. I saw Nanostray going cheap on Play.com and I thought I must buy it as this type of a game will be well suited for the DS format. There are 3 difficulties settings that you can choose from which are Normal, Advanced and Super. I found normal to be a little tricky to start with and also found myself wanting better weapons, but still managed to complete the levels on my last life just. As I flicked through the instruction booklet and came across the weapons page which tells you how to change your weapons on the touch screen. This made me laugh as there I was struggling a little to complete the levels on normal looking for weapon upgrades etc.
The graphics on Nanostray are excellent and very smooth running. At the end of each level you have a boss battle and once you have completed that level you then open up a high score tournament mode. Overall this is a good retro style shoot'em-up which could do with more levels and still a better selection weapons as Super Aleste had a massive display of weapons yet was still challenging.