If you want to play more than once a day, the app store has an almost identical free game called Wordlets, with 5, 6 & 7 word options. A whopping $1.99 to bin off the adds.
So there is 'Hard mode' this means you have to use any letters you have discovered, so this stops you using a new random word to eliminate letters. This is how I play anyway, but just in case I am now set to hard mode.