Hello, sneakyfletcher! There's a readme file that comes with the game with instructions on how you can transfer save files from the new demo to the full game. I'll copy paste them here for conveniency:
1. Go to to HEARTBEAT root folder and find the save folder. If you've downloaded on Windows, it should be like this:
[DEMO] > www > save
If downloaded on Mac, it should be like this:
[DEMO] > Game.app > Contents > Resources > app.nw > save
2. Grab the files from this folder and copy it into the same location for the new demo.
For windows: [FULL] > www > save
For mac: [FULL]> Game.app > Contents > Resources > app.nw > save
3. Once your save files are in the save folder, open the game normally and you'll be able to continue from where you left off on the demo.
We hope you enjoy the full game!!