My wife created simple symbol-letter decoders for my son. He thought they were a lot of fun and wanted to share them with friends, so I productized them. Screenshot here:
Simple, straightforward way to build fun little puzzles for kids. Play with it here. Besides changing the phrase, you can add additional confounding codes or remove codes to force kids to guess at the phrase. Then click the Print button and you’ll have a nice printout with the control panel hidden.
I’m building a 2-D version for the codes, too, so that will be along later this week.