The sprites for your game are great and I loved the guard's little 'look' animation when they stop - simple but worked really well for the style!
The gameplay was fun and you managed to put in a good number of mechanics considering the timeframe! I particularly liked the door code mechanic. It had me feeling pretty tense whilst trying to type it quickly without getting it wrong.
Overall it felt really well polished, with a some great mechanics, fun gameplay and nice artwork. Good job, it's a great entry ! :)