Null Cipher

NULL CIPHER
You are a codebreaker at Station Seven, the only signals-intercept post in a contested resource rich sector on the eve of collapse. Multiple factions are fighting over territory with each other and amongst themselves. And from somewhere beyond the region, transmissions are arriving in a cipher no one in this galaxy recognizes.

Real classical cryptanalysis

Substitution — The Kingdom's bureaucratic letter-for-letter swap.
Frequency analysis, common diagrams, patient inference.
Vigenère — The Federation's keyword cipher. Each noble house uses
its own keyword; learning the politics is part of the puzzle.
Columnar transposition — The Corporate Alliance's mechanical
scrambler. The same letters, reordered by a key permutation. Senior
executives use bigger grids.
Playfair — The Republic's 5×5 keyed-grid pair cipher. The hardest
of the classical four. Republic messages are rare; each is a project.
Trifid — The Fifth Power. Unknown to your hint manual until you crack
your first sample. The endgame.

Click a ciphertext letter. Every instance of that letter lights up at once.
Type your guess. The whole page updates simultaneously.

83 hand-authored messages reveal a sector arc across five chronological
Eras — The Stable Order, The Heat Rises, Things Get Strange, The Belt
Collapses, The Witness. Each Era unlocks as you decode half of the previous
one. Within an Era you choose what to crack and in what order. There is no
formal ending; the game finishes when you decide you are done.

Keyboard required. Patience recommended.