If the point of a demo is to sell you on a product, then Platinum Demo: Final Fantasy XV doesn't really live up to its name.
Released following the Final Fantasy XV Uncovered event, Platinum Demo makes only a half-hearted effort to let you know what FFXV is about. You play as a young version of Final Fantasy XV protagonist Noctis, navigating through a dreamscape and guided by a rather cute version of Carbuncle. What you're presented with is four distinct, unconnected scenes and a boss fight. In fact, you can probably finish the entire thing in 30 minutes tops.
Platinum Demo wants you to pre-order the game - as it makes clear on the opening screen and when you finish the final sequence - but it doesn't seem to contain many of the aspects that comprise Final Fantasy XV. There's no party, the available weapons are quite limited (two basic and two hidden weapons), and outside of the boss fight, combat is a simplistic. Within that boss fight, the game gives you little explanation, so if you haven't played the previous demo, Episode Duscae, you'll probably be hopelessly lost when it comes to the full combat mechanics.
Prior to the boss fight, combat feels weightless and unsatisfying. The basics feel somewhat like Kingdom Hearts, while not being as responsive. (Actually, the layout of the worlds feels a lot like Kingdom Hearts, too.) Weapon switching works, but for most of the demo, there's not much reason to do it. The magic system is quite powerful, but cumbersome to actually use. Dodging works, but dodge cancelling didn't seem as responsive as it was in Episode Duscae 2.0.
None of this is the real point though. In reality, Platinum Demo is tech demo. You'll wander from section to section, collecting crystals to unlock various plates found in each scene. The plates unlock upgraded versions of your starting weapons (the Toy Sword and Squeaky Hammer), the ability to turn into vehicles and an odd gazelle-like creature, enemy respawns, and more importantly, alternate world conditions.
Changing the time from day to night or the weather from rainy to sunny seems to be the real focus of Square Enix with this demo. Honestlyu, seeing that stuff in real-time is pretty cool. The first section even lets you summon a floating Leviathan or massive Titan, just to show off. Square Enix wants you to see what they've done with the Luminous Engine powering Final Fantasy XV.
The problem here is as a tech demo, Platinum Demo is really rough. The game seems to toggle anti-aliasing on and off depending on camera movement, resulting in some wildly divergent image quality. Sometimes a screenshot will look really good, but other times it'll looks like a mess. The lighting is great, but can also end up looking horribly washed out. And worst of all, the Platinum Demo seems to struggle to hold onto to 30 fps. Playing Platinum Demo has you jumping from highs to lows and back again on a regular basis.
One highlight is the absolutely great music. Yoko Shimamura is already putting in that work and the tunes in Platinum Demo feels suitably epic and "Final Fantasy". Looking forward to hearing the rest of her soundtrack in the finished game.
If you've already bought into Final Fantasy XV completely, Platinum Demo will be a visual guide to the world you can expect in the game. If you've played Episode Duscae 1 or 2, this will probably be enjoyable for you. If you're new to Final Fantasy XV, Platinum Demo is not the place to start. This is not the entry into Final Fantasy XV that's needed and Square Enix probably needs to think about putting Episode Duscae out there for people who haven't purchased Final Fantasy Type-0. That's a real demo with weight to it; this is just visual fluff for FFXV fans.