Hey thanks for the video and comments. Here are mine:

I like your idea about outlining the unpossessed equipment icons. As a matter of fact it would be more true to the original game.

There is no save bug, as you figured out. You just didn't push the right key in order to save the game.

You died during Mortarmech partly because you didn't notice you have an HP recovering spell...
Players must also keep an eye on their HP numbers. As Kazesui suggested I'll come up with something to make it more noticeable when HP is low.

Also, as you noticed, there is a pattern to the boss's claws and you can even check when the cannon is ready to fire by looking at the fuse.
This is not a game where rushing enemies and mashing the attack button will earn you victory (the original Crystalis wasn't like that either).
Players have to get the patterns down and plan their movements and attacks accordingly.

In order to enjoy the game more I suggest you take some time to kill enemies and reach LV 2 before fighting Mortarmech. You'll do twice as much damage to him that way.

Yeah so actually I don't think this video does Demo 0.1 justice. Game footage covered is only about 10% of what's in there and even then you missed a few things...
Nonetheless thanks for giving it a try and taking the time to make this video.