Managed to find 4 of the hidden messages. Could not find #5 or 6.
It is an interesting game, though I found the backtracking to be a bit excessive.
I noticed two bugs while playing:
* If you are hit while you warp from one room to the next, you can survive the hit.
* If you are at the save point prior to the top-left room (new area for the final 9 batteries), get hit and sent back, the music remains does not revert to what the current room's music should be.