Feistel Network 2D: Circuit & Avalanche Matrix

Most classical block ciphers, including DES, are built from a Feistel network: a block is split into two halves that swap places every round while one half is mixed with the other through a round function keyed off a schedule derived from a master key. This 2D build runs the exact same 16-bit Feistel cipher as its 3D counterpart — rotate, XOR with a round key, substitute through an S-box, permute — but visualizes it as a pannable signal-flow circuit plus a live Monte-Carlo matrix that measures, for every possible single-bit flip, how strongly each output bit responds. Watching the matrix wash out toward a uniform 50% shows, statistically rather than anecdotally, why a well-designed cipher makes one flipped input bit unpredictable in every output bit after only a few rounds.