Wow, for a first game, this has a really neat presentation! Not only is the art and music nice, it's also really well implemented with a good sense of pace. I expecially appreciated the way the story was told, and the transition between each "dimensions". Sure the mechanics are pretty basic, but the game has a solid direction and achieves to tell an engaging story. And even the puzzle, as simple as they are indeed, achieve to surprise and not feel laborious.
I still had one small issue though: it took me a while to understand how to interact with the locker! I didn't realized I could interact with the mouse, and even when I tried I first clicked directly on the number. There could be an indication somewhere (at least in the page description), because it almost blocked me. I'm glad I persevered to see the conclusion of the story!