Here's my thoughts after the first playthrough:
Music- Nice music selections. The overworld and each of the 3 'worlds' have their own themes. That's a nice little touch and the songs are pretty good, too.
Sound effects- There aren't very many here. Having a sword attack effect is good. Having a "you're hit" sound effect to go along with the blink is nice. What the game could use is another effect to indicate that you're hitting an enemy. I know that the enemy gives a little flash, but a sound effect here would have been nice, as well.
Controls- Controls are responsive and work well. Had no problems with the core moving mechanics: jumping, moving, and climbing. The sword has a little delay, but that actually works well. It's very much akin to the Castelvania whip in the slight delay. It's something that takes getting used to, but it's not a game-breaker at all.
Challenge- There isn't much of a challenge to this game. The enemies move in set patterns and don't do too much otherwise. The bosses aren't bad once you figure out their basic patterns and figure out that their invulnerability frames just get faster/ add more repetition (King K. Rool battle comes to mind).
Enemies- Enemies are ok, but get repetitive. Each world has its own set of enemies that seem to be based on something previously. Each world has a crawler, each one has a stationary spitter, etc.
Worlds- You have your forest world, your ruins level, and your temple level. Basic, but effective. :)
Shops- Shops are alright here, but you run into a problem of requiring a bunch of farming to unlock all of the medals. You need to buy 2 swords and 3 potions (could be off on the last number) to get 100% completion. This requires a lot of extra gameplay simply devoted to killing enemies and just trying to farm kupons. This is going to get very tedious and boring.
Advice for new players: 1) Save your bombs! You need them to get to chests. 2) Don't buy anything from the shops except for the pink life extending potions or the sword(s).
Overall: This is a pretty quick, easy platformer that's a nice play. It's not going to be 'Best on Newgrounds', but it's certainly better than a lot of content submitted to the site. It's a decent game that's worth a quick play.