four letter word puzzle

I've actually never heard of these types of puzzles before, but I found it very interesting when Bryan gave me a puzzle on a newspaper that him and his friends spent A LOT of time trying to figure out but couldn't. So he gave it to me to solve because he gave up.
It reminds me of Sudoku but I think it's way harder than Sudoku because I do not know every possible four letter word in the world.. which was why I was able to solve this with the assistance of the page on the internet with every possible four letter word. Cheating? I don't think so. I've never heard of the word eked or flue. If you know them, great. My vocabulary sucks and it's something I really want to expand on =]

Yes, I was so happy for solving it that I HAD to take a picture

Funny thing is that Bryan's closest answer was so close that all he had to do was switch the K and the E in the bottom left corner in his closest answer (written bellow the puzzle) in order for it to be solved. He didn't even use the internet for help like me.

For now, I'll just stick to Suduko ^^