You have a simple concept that's easy to grasp. Roll to get score, if you roll two 1's, you lose. I think it could use some more depth. Adding some function for the points could create a better feeling of loss when you roll a poor die, which in turn means the player would feel more tension when deciding whether to lock or to roll. As it is, locking doesn't feel much different from just losing. Either way, the game ends, why bother locking?