I've come up with a potentially novel Tetris variant. How would I perform a web search to determine if it is really novel?
Given the number of Tetris variants around, one might expect this to be difficult -- especially since my idea is quite close to a certain class of variants.
Perhaps a new kind of search engine is required?
http://en.wikipedia.org/wiki/List_of_Tetris_variants
You scroll down that list and try as many variants as possible. Maybe even keep a checklist of ones you have seen and a journal recording your findings. Basic research, you might even become an expert on Tetris; it's very easy to become an expert on something that you love, btw ;-)