I finished the fourth floor. I also put the key in the game. It hides itself in a room and your job once you get in the castle is to find it. It's your only way out of the castle: only when you defeat the giant will the exit show from the castle. But this blog entry is more about the beanstalk.
I figured I might put in the down part of the beanstalk since I didn't think it would take very long. Was I wrong! I had to go to sleep with semi-broken code at about 1 in the morning. I woke up this morning at about 10 and finished the rest of it. I had to figure out the way to make Jack appear at the top five screens ahead in the game. I had it working at four. Since I don't want to run the risk of breaking what I have, that's where I'll leave it at. So if Jack gets hit by a bat while going down the stalk (after defeating the giant), he'll wind up going up four screens. And if Jack goes up the beanstalk and gets hit by a bat (at the beginning of the game) he'll wind up going down four screens.
So the next time I work on this, I will begin work on the giant's room. I have around a whole unused bank to do this with, as planned. I have some idea on what I want to do and how to code it. I figure the only way Jack can move up and down is if he touches the ladder, which will be characters (the letter H, to be precise.) Since touching any character is meant as touching the character, I don't have to figure out where Jack's X position is.
The level will be set up like Donkey Kong, with giant boulders to avoid as you move up and down the screen. Oddly, this will be the only part of the game where you can use the Action button. It will be used for jumping, to jump over the boulders. The boulders will be sprites 2 and 3 (sprites 0 and 1 are Jack.) The ground will be the grid.