Scuffedcraft is very much in early development so there will be some bugs, and not all items are yet implemented. Remember to press TAB in game to save your progress. Clearing your browser data / cache / etc will delete your save data so keep that in mind.
After creating a world, refresh the page and you will see your world ready to play. For best performance, play this on google Chrome.
Experiment to see what different things you can make in Scuffedcraft :)