Gave this demo a try, I'll mostly be pointing out what I disliked in the hopes that the Steam version can improve on those areas.
1) As usual, bash the enemies with the attack button. The magic stat(called Special) is not worth investing, and it seems the demo doesn't have any spells I could unlock (hadouken doesn't count, its not cast by pressing D). In hindsight, I think part of why the complaints about mashing the attack button is common has to do with how the game teases you with the possibility of creating a magic-focused build, but end up needing to use regular attack all the time and having to grind enemies for random item drops to refill magic.
2) The hadouken is quite nice, but there are 2 major flaws. The white arrow is non-indicative of how much mana you'd spend to cast the ability, its only indicative for spells that don't exist in this demo. The other problem is that, I could get lulled into a false sense of security by charging the hadouken... only to find out just as I release the button that I am out of mana. The game should just tell me right off the bat that I cannot use the hadouken.
3) Blocking is practically useless. It only works against the 3 particular small projectile attacks, and even then it feels awkward. Either make it such that you can move very slowly while blocking or able to change direction, and make it more useful in general like reducing damage taken from an otherwise unblockable attack. It also doesn't help that blocking doesn't actually reflect projectiles; they don't do any damage, so you might as well just make the projectile disappear outright upon blocking. It also doesn't make intuitive sense for you to be able to block with your sword in a way that reflects projectiles, yet if you tried to attack a projectile nothing happens and you get hit.; this is why games usually give you a shield for blocking to indicate this is the case.
4) Generally bad camera relative to the game's feel. The fact that you had to include a dedicated "look up/down" button means the player has to look down every time he wants to go somewhere, when such a thing should be safely disregarded given the fast pace of the game. Where you need to go should be obvious without risking a sudden injury/death or having to slow down to a halt. I have no problems going up, its going down that gives problems because of this.
5) Misleading graphics - the foreground and the background sometimes look exactly the same. Prime examples are in the spike pit with the moving platform, and in the beginning of the phoenix dungeon where the statue is; the blue background combined with the bad camera and the feel of a fast paced feel of the game made me leap to my death many times. For the latter, it is not immediately obvious that I should jump on the statue itself in order to get up to the top, and even after that I find that elevator troublesome to jump onto. I mentioned earlier that blocking doesn't actually reflect projectiles. I've also tried to swing my sword at an enemy above me and my sword appears to connect, but it doesn't actually hit. Even the edge of the sword touching the enemy on level ground sometimes doesn't seem to connect.
6) Bad level design in Phoenix dungeon: the slammer traps. In one section of it, there is a whole row of slammers that slam down one by one rapidly. You expect the player to dash across, but at the end of the slammers, there is a worm, and you'd inevitably run into it. If you tried to slow down to deal with the worm or go back, you'll just get slammed. Basically, you have to know in advance to fire 1-2 hadoukens or wait for the enemies to slowly make their way towards you. It also doesn't help that you can dash into the slammers(which don't have any spikes on the side, mind you) before they've fully retracted and you still take damage as opposed to simply blocking your path.
I understand that this game is meant to be played on a controller, but sub-optimal keyboard controls is still no excuse; not all your players are going to play the game with a controller. I'll be using playstation lingo since that's the controller I'm familiar with:
* Menu screen - Apparently I have to press jump to get past the menu screen, which makes sense for a controller seeing as its on "X", but it makes zero sense for keyboard layout. You could just make both attack & jump proceed seeing as the attack button has no function in the menu anyway.
* Double-tap direction to dash - and given how tight jumping is in the game, this is way too hard to do. Make Q and E a dedicated dash button the same way a controller has the L & R back keys to work with. In any case, platform jumping is not a strong point of this game.
* Down is both the key for blocking and looking down - that's really disorienting; both buttons should be separate.
* Gamebreaking Bug: I was on the top left of the map, when I used Ctrl+Mousewheel to adjust my screen zoom on Chrome (I didn't want to use the full screen option). For some reason, I ended up outside the map and can no longer get back inside, my save file is ruined. I hope you have a failsafe in case something similar also happens on the Steam version.
* Hold UP while jumping. When you land, you're still in your falling animation. I should also note that apparently holding UP or DOWN will also lock your left/right controls, which is very unnatural.
Don't know if I missed anything, but in general you should take a page from Castle Crashers for some of the less intuitive parts of the game. I can't give it a high score due to the aforementioned issues and I'm judging this demo by its own merit; hopefully its better in the steam version.