This is a clever little offset 3 by 3 called the silver blocks or mirror blocks. It's sometimes called a bump cube.



It jumbles a bit when scrambled. Instead of solving for colour, you're solving for offset from the centre. However when you scramble it, you can only see the offset relative to other sides so it can take a long time to figure out which pieces go where. Other than delayed searching time, it isn't really harder than a regular cube.