This detects which keys you are pressing. It supports: 0-9 A-Z Arrows and space-bar Symbols can be added, but are buggy. Case sensing could be added as well, but would require a bunch of costumes.
Bug: Start holding a number, then hold shift, then let go of the number, then let go of shift. It seems to believe the key is still pressed. Also happens with symbols, although this project does not detect them.