This IFComp 2014 Twine game is mid-to-long in length. You wake up with amnesia in a judgment center reminiscent of the Cube movies. You choose to experience four challenges in an order of your choice.
Interestingly, each has its own genre. One is a locked room, one is related to a classic game theory scenario, one revolves around NPC interaction, and the last one ended before I really saw it.
The game has a bit of a prologue and an epilogue, as well.
I don't think it is possible to enter an unwinnable state.