The grid and the characters don't really match up. If you line up three Hs, stacked one on top of the other, in between the grid lines, it doesn't quite match up. I should know, I toyed around with this for about an hour trying to do this. As a result, I just gave up and decided to have the giant's room look like this:

Which is mostly what I had in mind when I thought this up. But there's one problem: It's not much of a screen. I may have to add some more levels. But first I have to code the game itself, which I will do later. And then if I have room left do that.

I had to be careful placing the Hs like this. The Odyssey 2 does not like characters overlapping and gives out garbled junk if they do. Fortunately, it looks just like this when I put the ROM on a real Odyssey 2.

But Jack isn't going to jump over the boulders. I decided it would be far less code (and more probability the game would work) if he simply ducked under them. Ducking will be done by pressing the joystick down. Up would make Jack go up the ladder if he's touching (and lined up with) it. So in all, Jack's collision detection would be between two things: a boulder and the ladders.