A quarter-tank warning that says it once, and a gauge that keeps saying it

Two halves of the same number. The warning is the moment it happened and
the colour is how things stand: it fires on the way down through a
quarter of a tank and then holds its peace, and the gauge stays red until
a base fills the lander up, which also allows the warning again.

Once, because a lander is at its most careful in the last few seconds
before it touches, and something repeating in its ear through that is not
a warning, it is a distraction.

Checked where the fuel actually moves rather than once a frame - the tank
only changes in takeFuel and payFuel, so there is nowhere else it can
cross a threshold.

Channel two, with the crash on three. Separate channels rather than one
reused, because a crash while the warning is still sounding should not cut
it off, and on a machine with four voices there is no reason to be clever.

Half and a tenth are the obvious next thresholds and are deliberately not
here: one is enough to find out whether being told at all is welcome.

---- And the crash sound is the one that was designed for it ----

Crash.json, which carries voice_gate itself, so the program's own trigger
write is gone - it would have masked a deliberate choice rather than
backing one up. The note moved from 24 to 60 by ear, and the comment
saying it was low went with it.

---- A check that could not tell a beep from a nag ----

Counting bursts of sound cannot: without the latch the warning fires
every tick the tank drops, far faster than the sound decays, so the beeps
run into each other and a burst counter sees one long burst either way.
It measures the LENGTH now - 26,944 samples against 490,348 - which is
the difference between six tenths of a second and ten seconds of it.

Programs/CosmOS/Apps/Lander.asm

@@ -80,7 +80,8 @@ start:
   CALL putLander
   CALL putGauge
   CALL putOrbital
-  CALL putBoom              ; The instrument, once, the way the tiles are.
+  CALL putBoom              ; The instruments, once, the way the tiles are.
+  CALL putAlarm
 
   INIA 0x01
   OUTA 0x02                 ; Key mode.
@@ -602,6 +603,25 @@ putGauge:
 ; Redrawn whole every frame. Thirty five cells is seventy bytes out of one port with the
 ; address named once, which is cheaper than working out which of them changed.
 showFuel:
+  ; ---- Green above a quarter, red below it ----
+  ;
+  ; The same number the alarm goes off at, so the sound and the picture agree. The sound is
+  ; said once and this stays said, which is the division of labour: one of them is the moment
+  ; it happened and the other is how things stand.
+  SETD.1 Fuel
+  LDA.1
+  INIB 0d64
+  CCF
+  SUB
+  BNC showFuelGreen
+  INIA 0x01
+  BRI showFuelColoured
+showFuelGreen:
+  INIA 0x02
+showFuelColoured:
+  SETD.1 GaugeColour
+  STA.1
+
   RSTA
   SETD.1 Fuel
   LDB.1
@@ -629,8 +649,9 @@ gaugeCell:
   STA.1
   INIA 0xC8
   OUTA 0xE9                 ; The solid block, which is the ground's tile.
-  INIA 0x02
+  SETD.1 GaugeColour
-  OUTA 0xE9                 ; Scheme two, so the bar is not the colour of the moon.
+  LDA.1
+  OUTA 0xE9                 ; Green, or red once a quarter is all that is left.
   BRI gaugeNext
 gaugeEmpty:
   OUTA 0xE9
@@ -1140,6 +1161,7 @@ takeFuel:
   BRA takeFuelNone
   DECA
   STA.1
+  CALL watchFuel            ; Checked where the tank actually moves, not once a frame.
   INIA 0x01
   RSTB
   CCF
@@ -2682,20 +2704,6 @@ putBoom:
   OUTA 0x41                 ; Channel three. Every parameter write below lands on it.
   SETD.0 BoomPatch
   CALL playPatch
-
-  ; ---- Struck, not held ----
-  ;
-  ; A gated voice lasts as long as something keeps hold of it, and the gate coming up is what
-  ; starts its release - which is what a keyboard is. A crash is not a keyboard. It is struck
-  ; once and then plays its own length, and nothing should have to remember to end it.
-  ;
-  ; Said here rather than left to the patch because it is the PROGRAM that knows this is a
-  ; one-shot: the patch decides what the bang sounds like, and this decides that it is a bang.
-  ; A patch designed in soundThing carries a gate of its own, and this overrides it on purpose.
-  INIA 0x51
-  OUTA 0x42
-  INIA 0x01                 ; Triggered.
-  OUTA 0x43
   RET
 
 ; ---- A whole patch, out of a table ----
@@ -2725,10 +2733,56 @@ playPatchOne:
 boom:
   INIA 0x03
   OUTA 0x41
-  INIA 0d24                 ; Low: the filter is doing the work and this is only the body.
+  INIA 0d60                 ; Middle C. The noise is not really pitched, but the filter is
+                            ; tuned off the note and this is where it was found by ear.
   OUTA 0x44                 ; Writing the note is what starts it.
   RET
 
+; ---- A quarter of a tank, said once ----
+;
+; ONCE, and that is the whole design of it. A lander is at its most careful in the last few
+; seconds before it touches, and something repeating in its ear through that is not a warning,
+; it is a distraction - so this fires on the way DOWN through a quarter and then holds its
+; peace. Filling up at a base allows it again.
+;
+; A quarter is 64 of 255. Half and a tenth are the obvious next two and are not here yet: one
+; threshold is enough to find out whether being told at all is welcome.
+watchFuel:
+  SETD.0 AlarmSaid
+  LDA.0
+  BNA watchFuelDone         ; Already said. Saying it again is what this exists to avoid.
+  SETD.0 Fuel
+  LDA.0
+  INIB 0d64
+  CCF
+  SUB
+  BNC watchFuelDone         ; No borrow: a quarter or more, so there is nothing to say.
+  INIA 0x01
+  SETD.0 AlarmSaid
+  STA.0
+  CALL alarm
+watchFuelDone:
+  RET
+
+; ---- The alarm, on channel two ----
+;
+; Effects count down from the top: the bang has three and this has two. They are separate
+; channels rather than one reused, because a crash while the warning is still sounding should
+; not cut it off - and on a machine with four voices there is no reason to be clever about it.
+putAlarm:
+  INIA 0x02
+  OUTA 0x41
+  SETD.0 AlarmPatch
+  CALL playPatch
+  RET
+
+alarm:
+  INIA 0x02
+  OUTA 0x41
+  INIA 0d72                 ; An octave over middle C, which is where a warning lives.
+  OUTA 0x44
+  RET
+
 ; ---- A key, or a button ----
 ;
 ; Somebody flying on a controller should not have to reach for the keyboard to say "yes, I
@@ -3309,6 +3363,11 @@ arriveNowhere:
 ; worth of adding is what says it went past, which is the same flag a sixteen bit sum uses to
 ; run one half into the other.
 payFuel:
+  ; Filled up, so the warning is allowed to come again. Eighty units always clears a quarter
+  ; tank, so this needs no test of its own.
+  RSTA
+  SETD.0 AlarmSaid
+  STA.0
   SETD.0 Fuel
   LDA.0
   INIB 0d80
@@ -3613,6 +3672,11 @@ FallAt:
 ; more arithmetic for a number nobody reads to the unit.
 Fuel:
   0xFF
+GaugeColour:
+  0x00
+; Whether the quarter tank warning has been given since the last time it was filled.
+AlarmSaid:
+  0x00
 GaugeLeft:
   0x00
 GaugeAt:
@@ -4093,3 +4157,5 @@ LanderArtAt:
 #Include math.asm
 
 #Include boom.asm
+
+#Include alarm.asm

Programs/Sounds/Crash.json

@@ -34,9 +34,11 @@
   "lfo0_rate": 8.796101,
   "lfo0_waveform": 0,
   "lfo0_active": 0,
+  "lfo0_mode": 0,
   "lfo1_rate": 1.000000,
   "lfo1_waveform": 0,
   "lfo1_active": 0,
+  "lfo1_mode": 0,
   "filter_cutoff": 13294.700195,
   "filter_resonance": 0.574200,
   "filter_type": 0,
@@ -46,6 +48,7 @@
   "filter_resModRouting": 0,
   "filter_resModDepth": 0.000000,
   "voice_levelSource": 2,
+  "voice_gate": 1,
   "master_volume": 1.000000,
   "master_pitchBendRange": 2.000000
 }

Programs/Sounds/alarm.asm

@@ -0,0 +1,58 @@
+; AlarmPatch, converted from Programs/Sounds/LowFuel.json by SoundPatch.
+; Designed in soundThing, where it can be heard. Do not edit the numbers
+; here: change the patch and convert it again.
+
+#Data
+
+AlarmPatch:
+  0d50                      ; how many pairs follow
+  0x00 0d1                ; oscillator 0, waveform
+  0x01 0d255              ; gain
+  0x02 0d128              ; duty
+  0x03 0d128              ; detune, in cents
+  0x04 0d130              ; octave
+  0x05 0d1                ; on
+  0x06 0d0                ; what moves its width
+  0x07 0d128              ; and how far
+  0x08 0d3                ; what moves its pitch
+  0x09 0d83               ; and how far
+  0x0A 0d1                ; what moves its gain
+  0x0B 0d255              ; and how far
+  0x10 0d1                ; oscillator 1, waveform
+  0x11 0d255              ; gain
+  0x12 0d128              ; duty
+  0x13 0d128              ; detune, in cents
+  0x14 0d128              ; octave
+  0x15 0d1                ; on
+  0x16 0d0                ; what moves its width
+  0x17 0d128              ; and how far
+  0x18 0d3                ; what moves its pitch
+  0x19 0d83               ; and how far
+  0x1A 0d1                ; what moves its gain
+  0x1B 0d255              ; and how far
+  0x20 0d4                ; amplitude envelope, attack
+  0x21 0d97               ; decay
+  0x22 0d255              ; sustain
+  0x23 0d33               ; release
+  0x30 0d9                ; modulation envelope, attack
+  0x31 0d90               ; decay
+  0x32 0d0                ; sustain
+  0x33 0d40               ; release
+  0x40 0d0                ; filter, on
+  0x41 0d0                ; type: 0 low, 1 high, 2 band
+  0x42 0d221              ; cutoff, in hertz
+  0x43 0d0                ; resonance
+  0x44 0d0                ; what moves the cutoff
+  0x45 0d128              ; and how far, in hertz
+  0x46 0d0                ; what moves the resonance
+  0x47 0d128              ; and how far
+  0x60 0d1                ; LFO 0, on
+  0x61 0d2                ; waveform
+  0x62 0d180              ; rate, in hertz
+  0x63 0d1                ; 0 free, 1 starts with a voice
+  0x70 0d0                ; LFO 1, on
+  0x71 0d0                ; waveform
+  0x72 0d127              ; rate, in hertz
+  0x73 0d0                ; 0 free, 1 starts with a voice
+  0x50 0d1                ; what shapes the level
+  0x51 0d1                ; 0 gated, 1 triggered

Programs/Sounds/boom.asm

@@ -1,11 +1,11 @@
-; BoomPatch, converted from Programs/Sounds/Crash1.json by SoundPatch.
+; BoomPatch, converted from Programs/Sounds/Crash.json by SoundPatch.
 ; Designed in soundThing, where it can be heard. Do not edit the numbers
 ; here: change the patch and convert it again.
 
 #Data
 
 BoomPatch:
-  0d47                      ; how many pairs follow
+  0d50                      ; how many pairs follow
   0x00 0d5                ; oscillator 0, waveform
   0x01 0d255              ; gain
   0x02 0d128              ; duty
@@ -49,7 +49,10 @@ BoomPatch:
   0x60 0d0                ; LFO 0, on
   0x61 0d0                ; waveform
   0x62 0d220              ; rate, in hertz
+  0x63 0d0                ; 0 free, 1 starts with a voice
   0x70 0d0                ; LFO 1, on
   0x71 0d0                ; waveform
   0x72 0d127              ; rate, in hertz
+  0x73 0d0                ; 0 free, 1 starts with a voice
   0x50 0d2                ; what shapes the level
+  0x51 0d1                ; 0 gated, 1 triggered

Tests/expected/cosmosCrossDisk.out

@@ -25,7 +25,7 @@ Mode.sbx                48
 Flip.sbx                173
 Sprite.sbx              442
 Depth.sbx               672
-Lander.sbx              8409
+Lander.sbx              8608
 Pad.sbx                 264
 Crash.sbx               632
 vars.script             50

Tests/expected/cosmosDrives.out

@@ -15,7 +15,7 @@ Mode.sbx                48
 Flip.sbx                173
 Sprite.sbx              442
 Depth.sbx               672
-Lander.sbx              8409
+Lander.sbx              8608
 Pad.sbx                 264
 Crash.sbx               632
 vars.script             50

Tests/expected/cosmosFault.out

@@ -32,7 +32,7 @@ Mode.sbx                48
 Flip.sbx                173
 Sprite.sbx              442
 Depth.sbx               672
-Lander.sbx              8409
+Lander.sbx              8608
 Pad.sbx                 264
 Crash.sbx               632
 vars.script             50

Tests/expected/cosmosFlip.out

@@ -22,7 +22,7 @@ Mode.sbx                48
 Flip.sbx                173
 Sprite.sbx              442
 Depth.sbx               672
-Lander.sbx              8409
+Lander.sbx              8608
 Pad.sbx                 264
 Crash.sbx               632
 vars.script             50

Tests/expected/cosmosGrid.out

@@ -22,7 +22,7 @@ Mode.sbx                48
 Flip.sbx                173
 Sprite.sbx              442
 Depth.sbx               672
-Lander.sbx              8409
+Lander.sbx              8608
 Pad.sbx                 264
 Crash.sbx               632
 vars.script             50

Tests/expected/cosmosMonitor.out

@@ -108,7 +108,7 @@ Mode.sbx                48
 Flip.sbx                173
 Sprite.sbx              442
 Depth.sbx               672
-Lander.sbx              8409
+Lander.sbx              8608
 Pad.sbx                 264
 Crash.sbx               632
 vars.script             50

Tests/expected/cosmosMonitorRun.out

@@ -27,7 +27,7 @@ Mode.sbx                48
 Flip.sbx                173
 Sprite.sbx              442
 Depth.sbx               672
-Lander.sbx              8409
+Lander.sbx              8608
 Pad.sbx                 264
 Crash.sbx               632
 vars.script             50

Tests/expected/cosmosRun.out

@@ -15,7 +15,7 @@ Mode.sbx                48
 Flip.sbx                173
 Sprite.sbx              442
 Depth.sbx               672
-Lander.sbx              8409
+Lander.sbx              8608
 Pad.sbx                 264
 Crash.sbx               632
 vars.script             50

Tests/expected/cosmosSlowDisk.out

@@ -13,7 +13,7 @@ Mode.sbx                48
 Flip.sbx                173
 Sprite.sbx              442
 Depth.sbx               672
-Lander.sbx              8409
+Lander.sbx              8608
 Pad.sbx                 264
 Crash.sbx               632
 vars.script             50

Tests/expected/cosmosSprite.out

@@ -22,7 +22,7 @@ Mode.sbx                48
 Flip.sbx                173
 Sprite.sbx              442
 Depth.sbx               672
-Lander.sbx              8409
+Lander.sbx              8608
 Pad.sbx                 264
 Crash.sbx               632
 vars.script             50

Tests/video.sh

@@ -2714,6 +2714,70 @@ EOT
     && result ok "and it is loudest at the front" "which is what makes it a bang" \
     || result no "and it is loudest at the front" "louder in the second half than the first"
 
+# ---- A quarter of a tank, said once ----
+#
+# ONCE is the whole design of it. A lander is at its most careful in the last few seconds
+# before it touches, and something repeating in its ear through that is not a warning, it is a
+# distraction. So it fires on the way DOWN through a quarter tank and then holds its peace,
+# and filling up at a base allows it again.
+#
+# The gauge says the same thing the other way round: the sound is the moment it happened, the
+# colour is how things stand. Both off the same number, so they cannot disagree.
+python3 -c "
+import struct
+# Seventy of two hundred and fifty five, which is a few ticks of thruster above the quarter.
+open('$BUILD/lowfuel.state','wb').write(struct.pack('<hhhhhhBBBB',
+    0x14A0, 0, 0, 0, 0x14A0, 2600, 70, 0, 0, 0))
+"
+cp "$ROOT/Tests/build/disks/cosmos.img" "$BUILD/lowfuel.img"
+"$ROOT/SplitDisk" put "$BUILD/lowfuel.img" "$BUILD/lowfuel.state" /lander.state > /dev/null
+python3 -c "open('$BUILD/burn.pad','wb').write(b'\x08' * 40000)"
+for when in 1700000 2400000; do
+    timeout 60 "$EMU" --fast --cycles $when --keyboard "$BUILD/fly.keys" \
+        --pad "$BUILD/burn.pad" --screen "$BUILD/fuel$when.ppm" \
+        --disk "$BUILD/lowfuel.img" --ram-disk 2048 \
+        "$BUILD/cosmos.bin" > "$BUILD/fuel.out" 2>&1 || true
+done
+timeout 60 "$EMU" --fast --cycles 12000000 --keyboard "$BUILD/fly.keys" \
+    --pad "$BUILD/burn.pad" --sound "$BUILD/warn.raw" \
+    --disk "$BUILD/lowfuel.img" --ram-disk 2048 \
+    "$BUILD/cosmos.bin" > "$BUILD/warn.out" 2>&1 || true
+read -r ABOVE BELOW WARNINGS <<EOT
+$(python3 -c "
+def gauge(path):
+    d = open(path, 'rb').read()
+    width = int(d[:40].split()[1])
+    px = d[d.index(b'255\n') + 4:]
+    def cells(colour):
+        c = bytes.fromhex(colour)
+        # The top row of the window, which is where the gauge is drawn.
+        return sum(1 for i in range(len(px) // 3)
+                   if px[i * 3:i * 3 + 3] == c and i // width < 8) // 64
+    return '%d,%d' % (cells('50c050'), cells('d04038'))
+import struct
+raw = open('$BUILD/warn.raw', 'rb').read()
+s = struct.unpack('<%dh' % (len(raw) // 2), raw)
+# ---- HOW LONG it sounds for, not how many times it starts ----
+#
+# Counting bursts cannot tell one beep from a nag. Without the latch the warning fires on
+# every tick the tank goes down, which is once every ten frames - far faster than the sound
+# decays, so the beeps run into each other and a burst counter sees ONE long burst either way.
+# The length is what differs: six tenths of a second against ten seconds of it.
+loud = [i for i, x in enumerate(s) if abs(x) > 300]
+span = (loud[-1] - loud[0]) if loud else 0
+print(gauge('$BUILD/fuel1700000.ppm'), gauge('$BUILD/fuel2400000.ppm'), span)
+" 2>/dev/null || echo "none none -1")
+EOT
+# Green cells then red cells, and none of the other colour either time.
+[ "$ABOVE" = "8,0" ] && [ "$BELOW" = "0,7" ] \
+    && result ok "the fuel gauge goes red at a quarter" "eight green became seven red" \
+    || result no "the fuel gauge goes red at a quarter" "$ABOVE above, $BELOW below"
+# Twelve seconds of holding the thruster, which empties the tank entirely and keeps it empty.
+# The warning is under a second of that, or it is a nag rather than a warning.
+[ "$WARNINGS" -gt 0 ] && [ "$WARNINGS" -lt 48000 ] \
+    && result ok "and the warning sounds once, not once a tick" "$WARNINGS samples of it in twelve seconds of running dry" \
+    || result no "and the warning sounds once, not once a tick" "$WARNINGS samples of warning"
+
 # ---- Dust on landing, and gas on letting go ----
 #
 # The same six pieces as the explosion, thrown differently: dust goes sideways and UP off the