- Just One More Level!: Especially if you're into mathematics.
- Scrappy Mechanic: Wolfram Alpha's mathematics engine is essentially a limited version of Mathematica, so it would make sense if it wouldn't be able to understand equations beyond a certain complexity. However, it seems instead that whether or not Alpha accepts a given query is entirely random. You can put in a complicated query and Alpha will understand it just fine, but make one tiny, minor edit (e.g. change "2x" to "3x") and all of a sudden the program refuses to comprehend it.
YMMV / WolframAlpha