Tap code decode
Tap code decode, classical cipher, a puzzle not a protection, computed on your device. Output is uppercase letters only, since tap groups carry no case, spacing or punctuation.
Tap code decode splits your input on slashes into row-dots and column-dots pairs, then looks each pair up on the unkeyed 5 by 5 square. Every group must be exactly two dot runs of 1 to 5 dots, and a malformed or out-of-range group is refused by its position. Output is uppercase letters only, with no case, spacing or punctuation recovered.
Questions
What input format does it expect?
Groups of row-dots and column-dots separated by a space, with groups themselves separated by a slash.
What counts as a malformed group?
Anything that is not exactly two runs of dots, or a run outside 1 to 5 dots; both are refused with the group's position named.
Why is my output uppercase with no spacing?
Because tap code only carries the 25 letters; case, spacing and punctuation were never encoded to recover.
What happens to J?
It never appears; that position always decodes as I.
Can I use this from the command line?
Yes, it runs the same on the page, the CLI and MCP.