The canal that wouldn’t forget your last stroke
Just after sunrise, I slid a rowing boat into a narrow canal. One hard stroke sent ripples to both walls. A moment later, the waves came back and gave the hull a shove, even with my oar in the air. The canal wasn’t done with my last move.
It’s tempting to act like the water forgets straight away, so every stroke meets calm water. That works when things are gentle. But strong strokes, slow swirls, and little side inlets keep old waves alive. Some tiny devices have surroundings that behave like this canal.
So I stopped trying to guess from “right now” alone. I wanted a reusable canal guide: choose any run of strokes, taps, pauses, even a full reset, and the guide tells how the boat will sit after each choice. The point is simple: it predicts sequences when the canal remembers.
Making that guide meant splitting causes in two. One part is the boat reacting to my oar. The other part is the canal carrying leftover ripples forward, then feeding them back later. Strokes match the actions you choose, the canal matches the surroundings, and the returning shove is memory linking different moments.
At first it felt too big to write down, because there are endless stroke patterns. Then I noticed most waves fade. Only a short window of the past still matters, so the guide can be kept as a chain of small linked pieces. In friendly canals, the same kind of link repeats as time passes.
With that compact guide, I could try whole rhythms quickly, not just single strokes. I could ask how a tap now changes what a later tap does. Before, the canal’s pushback was a nasty surprise. Now it was something I could plan around and reuse.