-Very polished, love the intro and the music.
-Resource pack check works well.
-It isn't immediately obvious to the player that clicking the sign changes the difficulty level.
-Sword to cut leaves doesn't actually cut all leaves. There doesn't seem to be a visual distinction for which

can be cut.
-Some lagspikes. Not sure if avoidable.
-Transposition orb is a cool way to make a co-op map playable with one player.
	-And the timer makes it so players don't accidentally use it when scrolling over hotbar.
-Intro is a good use of "Show, don't tell".
-Cool, falling gravel physics puzzle! Haven't seen that in forever.
-Possible to create a softlock by accidentally dropping sword.
-There's a button here. Not sure if it does anything.
-Without any food or saturation, starving to death happens pretty quickly.
	-Actually, the first boss fight is basically impossible given the constant poison potions and no

regenning health due to hunger dying almost immediately. I had to open to lan and cheat here in order to give

myself saturation.
-I missed the intro to Chapter 2, since I'd paused and my game was still "open to lan" from earlier. Not your

fault, but I'm noting it here just in case.
-Heh. Windows startup sound.
-Sensory deprivation parkour is a cool idea.
-I fell off of here while my coal was placed elsewhere and softlocked the game. http://i.imgur.com/bHhufQR.png
-Typo. http://i.imgur.com/bwMAucA.png
-Was that missile I picked up actually used anywhere? I mean, I fought missiles, but I don't remember ever

actually using the one that I had. It was in an out-of-the-way place, so maybe I was accidentally sequence-

breaking?
-I like the health feedback on the final boss. Why wasn't it used on the other ones, though?
-The use of colored outline to show her next attack was helpful. The fireballs were still usually too far away

for me to deflect, though.
	-To be specific: Since the fireball launch location appears to be random, the time between when the

fireball is launched and when it hits the wall is usually not enough time to actually reach a fireball to

deflect. This leaves it feeling more like a game of roulette than a boss battle. Maybe if there were some way to

predict where the fireballs will be, or launch one at the player?
	-Since the skeleton attack is a three-hit kill (and the only attack that isn't easy to survive), it

winds up being a game of hoping you get enough fireballs to actually deflect three before he uses the skeleton

attack.
	-This stacks with the hunger issues mentioned earlier. Losing a boss battle to a single hit simply

because the boss took so long to be vulnerable that you ran out of hunger doesn't feel fair, especially when it

means you have to restart the whole thing.
-Fireball deflection sometimes failed if I was too close to the witch. This is an issue because being really

close to the witch is the only way to consistently get a decent fireball deflection.
-Maybe not strictly speaking a typo, but somewhat awkward wording?

Regarding the backend:
-A bit nitpicky, but you've left TrackOutput on on every command block I could find. This combined with the fact that you have most of your redstone within the player-loaded area and are most likely well beyond the "63" rule in certain places means that, in co-op, the map would probably have unplayable lag issues in certain areas. Normally I don't care about backend stuff so long as it works well, but this is a fairly serious issue. I'd advise running Texelelf's "FixLag" filter to disable the trackoutput on all of your command blocks. It'll prevent block update ticks from being sent to the clients, as well as the chunk updates most likely sent in cases where more than 63 blocks are run in a given chunk on a given tick.