Make the aircraft breathe, and send a ring out from each of them

Two things that move on their own, on the window and in the animated
pictures alike, and both turned off with a flag.

An aircraft swells from bright to dim and back.  At the top of the swell it
burns: drawn in a set of peak colours and wearing a halo, which is what a
phosphor does when the beam sits in one place a little too long.  The halo
is the aeroplane's own shape spread outward a pixel at a time rather than a
circle drawn round it -- the first attempt did draw a circle and it looked
exactly like what it was, a ring of dots -- so the glow has the shape of the
thing casting it.  It goes only where the picture was still empty, over the
ground and the grid and the background and never over another aircraft,
since a halo is what light does to the dark around a thing.

And a ring leaves each aircraft and travels outward, growing and dimming as
it goes.  What a radar repeater does, and what the eye reads as this thing
is transmitting -- which is exactly what an aeroplane on this picture is
doing, twice a second, and is how it got on the picture at all.  One ring at
a time per aircraft: a new one leaves as the last reaches the end of its
reach, so the sky has one ring per aeroplane rather than a stack of them to
read through.

Five settings, in a group of their own because the others were already at
eight: whether to pulse, how long a swell takes, whether to echo, how long
between rings, and how far a ring gets.  Both times are seconds of watching
rather than of flying, so the rhythm looks the same whatever speed an
evening is being run through.

Two decisions worth naming.  Each aircraft is offset by its own address, so
a sky full of them swells and rings separately rather than beating as one,
which would read as a display flashing rather than as a lot of separate
things transmitting; the offset comes from the address, so an aeroplane
keeps its rhythm from one frame to the next and from one drawing of the same
log to the next.  And only an aircraft still being heard pulses: one that
has gone quiet is already fading, and a thing that is fading and beating at
once says two contradictory things about itself.

The window can blend and its swell is continuous.  The animation cannot, a
GIF being indexed colour, so there the swell is the steps a palette allows
-- which family of colours the aeroplane is drawn from, and how far its halo
reaches, which is six between them and reads as a swell at a couple of
seconds a cycle.  The peak has sixteen colours of its own, sixteen being
exactly what was left of the palette once 255 is set aside as the
transparent index.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016PsWPTweCT6pwxKngvVxcg

packaging/make-man.py

@@ -1102,6 +1102,37 @@ Every option the ADS-B side takes, in the six groups the menu shows them in.
 Each is a flag here and a line in the menu, and both come from one table in
 the program, so they cannot disagree.
 .AIRCRAFT_OPTIONS_HERE
+.SS Pulsing and echoes
+.B \-\-pulse
+swells each aircraft from bright to dim and back. At the top of the swell it
+burns: drawn in a set of peak colours and wearing a halo grown out of its own
+shape, which is what a phosphor does when the beam sits in one place a little
+too long. The halo is the aeroplane itself spread outward a pixel at a time
+rather than a circle drawn round it, so the glow has the shape of the thing
+casting it, and it goes only where the picture was still empty.
+.PP
+.B \-\-echo
+sends a ring travelling outward from each aircraft, growing and dimming as it
+goes \[em] what a radar repeater does, and what the eye reads as this thing is
+transmitting, which is exactly what an aeroplane on this picture is doing
+twice a second. One ring at a time per aircraft.
+.PP
+.BI \-\-pulse\-rate " SECONDS" ,
+.BI \-\-echo\-every " SECONDS"
+and
+.BI \-\-echo\-size " PIXELS"
+set the rest. The two times are seconds of watching rather than of flying, so
+a pulse looks the same whatever speed an evening is being run through. Each
+aircraft is offset by its own address, so a sky full of them swells and rings
+separately rather than beating as one, and an aeroplane keeps its own rhythm
+from one drawing of the same log to the next. Only an aircraft still being
+heard pulses: one that has gone quiet is fading, and a thing that is fading
+and beating at once says two contradictory things about itself.
+.PP
+The window can blend and its swell is continuous. The animation cannot, a GIF
+being indexed colour, so there the swell is the handful of steps a palette
+allows \[em] which family of colours the aeroplane is drawn from, and how far
+its halo reaches.
 .SS Range rings
 .B \-\-rings
 puts faint discs at a quarter, a half and three quarters of the radius,