So I decided to cancel my Odyssey 2 doodle and instead work on the Game Boy game that inspired it. I decided instead of it saving your progress, to make it have passwords instead. Now it will be easier to publish when/if it gets finished because it doesn't need a battery.
As a kid I wondered why every game didn't just save your progress because it was possible on some. Now I know why: To keep costs down. I tried to make the password minimal. It's 8 button presses on a special password screen. I also made it so it displays the password on the screen. Fortunately I had some room left on the screen to do that.
So the next time I continue work on this, the next things to do are make the password screen song and work on level 30. My ultimate goal is to make 50 screens. Not as many as Chip's Challenge's 99 screens, but I'm only one guy working on this. And it's hard to design these levels in the first place.