Go through the door straight ahead. Then go through the door to the top-right. Go through the leftmost door and get the map from the chest, then go up and open chests etc. as you go. You'll find 100 rupees in the middle chest and 300 in the top chest.
Now go back to that bottom-right shutter door. The opening function is lost to us, so walk around it and the game will scroll the screens. Bomb the right-hand wall for 100 rupees.
You don't have a key, so again go around the door. The camera won't follow you correctly, but walk to the right straight after entering and it will scroll and reset the view. There's that key! If you want to play honestly, go back and use the key on the door (to your bottom left right now) or you could keep it for a later door. Whatever you do, DO pick it up as it raises your score! Go down the stairs to B1. I recommend NOT using it as you need it very soon for the door it was most likely intended for.
Go down until you see a door, then go through it. DO NOT use the stairs as they put you on the wrong plane.
Bomb the top wall for a thief who upgrades your arrows for a mere 100 rupees. Go through the left door.
Go through the bottom door, ignoring the fire-chain thing, and watch for the spiked thing in the next room. Go through the left-most door.
Pull the statue's tongue for a chest containing the Boss Key! Now go right, up, left to get to the steel ball room. The left pot has a button to open the door if you wish. Anyway, choose your moment (listen for silence) and run across. Go down the stairs to B2.
If you have the key, open the door and go through. If not, walk down to one side of it and keep going down until the screen scrolls, then scroll up again to fix it.
WARNING: YOU MUST light the torches to open the chest OR YOU CRASH THE GAME! Then go down the stairs and collect your key.
In the next room, the left chest has the Flame Shield and the right has the Compass. There are other rooms down here, but their contents appear to be lost. Now backtrack up to the floor above and to the room with the fire chain thing. Go up and open the chest for the Hookshot! One of my favourite ALttP items :)
Now go down and to the right and get to the stairwell to go to the Boss' floor (check your map).
Now go down and right and through the door, and through the door to the left. Unlock the Boss Door and go in. Weave your way up to the Boss Door at the top left, grabbing stuff from surrounding pots until you have refilled everything.
This boss fight is made more annoying than it should be by the fact that the boss can escape offscreen. Do your best to keep close to him so he'll do his "spin ball bits around body" move; then close in (even if it means taking damage) and slash him as fast as possible. Also try to Hookshot off as many of his ball bits as possible. If he goes off the current area you can scroll a surprisingly long distance vertically, but if he's really gone you'll have to leave the room and come back again, which means losing any progress you made on defeating him.
The Yak submits this sneaky strategy, if you don't mind "cheating"...:
- "In dungeon 4, I have another strategy for the boss fight. It's helpful to have an extra potion for this. Upon entering the boss room, make the boss go up so he's just off the screen and go after him (so that he is never more than one or two blocks about the top of the screen. There's a glitch where the game thinks the blobs around the boss are gone, even though they are there. The boss will jump in the air and jump back down. When this happens, stay below the boss on the screen. The boss will start swimming down (almost always down). hit the boss with your sword and keep below the boss (making sure you don't leave the screen.) After a few hits, you've won. It's simpler than using the hookshot to take off all the blobs. (Use a glitch in the game to bypass missing data)"
Well, that works very well indeed! Be careful when the boss swims downwards as you must stop him doing this or you may lose him. Also be aware that the blobs will relocate. Since the game thinks they aren't attached when the boss jumps up and splashes down somewhere else the blobs will teleport instantaneously to his new location--they actually get there before he does. So watch out!!!