A moon has no air, so a sideways drift never stops by itself and stopping
one means cancelling the velocity EXACTLY. That is not hard to do; it is
hard to do blind, which is what it was - a number nothing on the screen
said anything about.
So sprite one is a bar whose width is the drift. It runs right from the
middle of the screen for a rightward one and left for a leftward one, so
which way is as plain as how fast, and stopped is the one state with
nothing drawn at all. The whole of it is a target width written once a
frame; the device stretches one tile into it and the program draws
nothing.
Sideways thrust is one a tick rather than two. At two, the smallest
correction available was twice the size it needed to be and overshooting
was the normal outcome.
WHICH ZERO MEANS NOTHING TURNED OUT TO MATTER. A target width of nought is
the NATURAL width, not an empty sprite - so a bar with no drift in it came
out eight pixels wide, sitting at the middle of the screen, saying
"stopped" in the same shape it says "drifting slightly". What draws
nothing is a SIZE of nought, which is the other zero in the other byte.
Both meanings are deliberate and documented and it still caught me out
inside a week of writing them down.
The check for it earned its place by failing on that before it was found,
which is the best evidence a check can offer.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
AnachronautandClaude Opus 5
db0c26e13f