If you ever made a full game, I think this has potential for a bigger game, you can do more with the age mechanic and things being different now as opposed to the past, like object don't exist anymore, but you can go back and use them; things that you remember wrong, as you know many people see the past with nostalgia glasses that don't let them see its flaws.
As for the current version of the game, I think that fact that you can hold the jump button and keep jumping is a bit off, I fell off a pit a couple of times because I was not expecting my character to keep jumping; and in one part, I pressed a switch/button, and I wasn't sure it did something because the light didn't seem to change to be walkable, it did, but it was hard for me to see at first because the change was very small and the light was off-camera when I pressed the switch, so I got stuck for a minute. Also I would like to be able to jump with the UP arrow, that would be a bit easier for me at least. Other than that the game was amazing, loved the message, I really enjoyed myself, keep it up!