Flag semaphore is a technique used for visual communication, where the positions of two flags represent a single letter.
I often see these at puzzle hunts disguised as clock hands, tree branches, dance moves, etc., and I'm very slow at reading the lookup chart (see image at right). I thought the ideal way to decode semaphore would be to draw out the actual angles. So I wrote my own visual semaphore decoder, implemented using Vue.
It's very rare to solve just one semaphore - usually you need to solve many to form a word or a phrase. So I added the ability to push each letter to a text box, using . (period) for quick entry. It's a regular text input, so you can type normally if you want to change anything.
There is also a quick link to anagram the resulting letters on Nutrimatic, which is a very powerful pattern-matching tool. If you're familiar with Nutrimatic syntax, you can use it here as well - for example, if you're not quite sure what a semaphore position is, you can enter capital A for "any letter", and hope that Nutrimatic will be able to fill it in for you.
Note that this decoder does not decode numerals, which are typically represented with the (0, 45) signal followed by another signal.
More writing on how this project was made:
The Making of Semaphore Decoder.