Footle is not a feature-rich puzzle. However, it has a dark mode and a hard mode. The hard mode is for people who love tough challenges. You will have to play with the correct letters on subsequent guesses in this mode. For instance, if you start with the letter D and it is green, you will have to keep playing with the same letter from then on. And, if you have the letter S in the word and it is yellow, then all your subsequent guesses should include the letter S somewhere.