sound.ref

[Audio:fire:Missile fire]
This sound effect is produced by the routine at #R$8A02 when the player fires
the missile. It plays 8 speaker pulses (~1.3 ms) per interrupt for 7
interrupts (~140 ms total), with ~18.7 ms gaps between calls.

The call count comes from missile physics: the missile spawns at Y=126 and
moves 6 pixels per animate pass, with the sound flag cleared when Y drops to
112 (after 3 passes: 126→120→114→108). At 50 Hz with 2 animate passes per
frame at ~12 FPS: 3 × 50 / (2 × 12) = 6.25, rounded to 7.

#AUDIO0(fire.wav)(#INCLUDE(FireDelays))

[Audio:engine-normal:Engine (normal speed)]
This sound effect is produced by the routine at #R$6C5D during normal speed
flight (player not pressing up or down). Called once per interrupt (~50 Hz);
each call plays 8 speaker pulses (~9.5 kHz).

Note: the period parameter is <code>sound_flags AND $0F</code>, which equals 2
during normal speed gameplay. With period = 2, the ON and OFF delays are 49T
and 63T respectively. At 44,100 Hz, 49T converts to 0.62 samples and 63T to
0.79 samples — both round to 1 sample, producing alternating single-sample
pulses at 22 kHz (the Nyquist limit), which are effectively inaudible as PCM.
The delays here use period = 10 (177/191 T-states, ~2.2/2.4 samples each) to
produce a representable, audible illustration.

#AUDIO0(engine-normal.wav)(43,[177,191]*7,177,[67092,[177,191]*7,177]*49)

[Audio:engine-fast:Engine (fast speed)]
This sound effect is produced by the routine at #R$6CB8 when the player holds
up to accelerate. Called once per interrupt (~50 Hz); each call plays 8
speaker pulses (~16.6 kHz).

#AUDIO0(engine-fast.wav)(43,[113,98]*7,113,[68255,[113,98]*7,113]*49)

[Audio:engine-slow:Engine (slow speed)]
This sound effect is produced by the routine at #R$6CD6 when the player holds
down to decelerate. Called once per interrupt (~50 Hz); each call plays 8
speaker pulses (~10.3 kHz).

#AUDIO0(engine-slow.wav)(43,[113,226]*7,113,[67359,[113,226]*7,113]*49)

[Audio:explosion:Explosion]
This sound effect is produced by the routine at #R$6C7B when the player's plane
is destroyed. The ON delay varies semi-randomly between frames because the DE
register is not intentionally set by the caller, giving the explosion its noisy
character. Each frame plays 4 cycles of waveform with a decreasing OFF delay,
making the sound more rapid and urgent as the explosion progresses.

#AUDIO0(explosion.wav)(#INCLUDE(ExplosionDelays))

[Audio:low-fuel:Low fuel warning]
This sound effect is produced by the routine at #R$6CF4 when the fuel level
drops below the warning threshold. The pitch warbles by decrementing the period
each frame, creating an urgent rising tone that resets after reaching zero.

#AUDIO0(low-fuel.wav)(#INCLUDE(LowFuelDelays),67000,#INCLUDE(LowFuelDelays))

[Audio:bonus-life:Bonus life]
This sound effect is produced by the routine at #R$6C31 when the player earns
an extra life. It generates a rising pitch over 63 frames by calling the ROM
BEEPER routine at <code>$03B5</code> with decreasing pitch values.

#AUDIO0(bonus-life.wav)(305,[8303]*3,[44908,[8303]*3]*7,[47980,[7279]*3]*8,[51052,[6255]*3]*8,[54124,[5231]*3]*8,[57196,[4207]*3]*8,[60268,[3183]*3]*8,[63340,[2159]*3]*8,[66412,[1135]*3]*7)

[Audio:fuel-full:Tank full]
This sound effect is produced by the routine at #R$6E92 when the fuel tank is
already full and cannot accept more fuel. Called once per game frame (~12 FPS);
plays a short beep (~1450 Hz, ~6 ms) via the ROM BEEPER routine.

#AUDIO0(fuel-full.wav)(218,[1207]*17,[270463,218,[1207]*17]*4)

[Audio:refuel:Refueling]
This sound effect is produced by the routine at #R$6E50 while the plane is
actively receiving fuel. Called once per game frame (~12 FPS); uses the ROM
BEEPER routine with <code>DE=$0007</code>, <code>HL=$0333</code> (8 cycles, ~516 Hz, ~14.6 ms per call).

#AUDIO0(refuel.wav)(218,[3391]*15,[240117,218,[3391]*15]*4)

[Audio:heli-missile-launch:Helicopter missile launch]
This sound effect is produced by the routine at #R$73EB when an advanced helicopter
fires a missile. Uses the ROM BEEPER routine with <code>DE=$0001</code>, <code>HL=$2800</code> (2 cycles,
~43 Hz, ~35 ms).

#AUDIO0(heli-missile-launch.wav)(218,[41075]*3)

[Audio:shell-whistle:Tank shell whistle]
This sound effect is produced by the routine at #R$7457 once per game frame while a
tank shell is in flight. The pitch parameter is HL = step × 256 (<code>DE=$0002</code>, 3 cycles
per step), producing a descending whistle over trajectory steps 1–7. Step 8 triggers
an explosion and plays no sound.

#AUDIO0(shell-whistle.wav)(#INCLUDE(ShellWhistleDelays))

[ExplosionDelays]
121,[657,412]*3,657,
67000,[1169,396]*3,1169,
67000,[401,380]*3,401,
67000,[913,364]*3,913,
67000,[657,348]*3,657,
67000,[1041,332]*3,1041,
67000,[785,316]*3,785,
67000,[785,300]*3,785,
67000,[785,284]*3,785,
67000,[1041,268]*3,1041,
67000,[1169,252]*3,1169,
67000,[657,236]*3,657,
67000,[657,220]*3,657,
67000,[1041,204]*3,1041,
67000,[529,188]*3,529,
67000,[657,172]*3,657,
67000,[401,156]*3,401,
67000,[1169,140]*3,1169,
67000,[273,124]*3,273,
67000,[1169,108]*3,1169,
67000,[913,92]*3,913,
67000,[529,76]*3,529,
67000,[657,60]*3,657

[LowFuelDelays]
66,
2033,2088,2017,2072,2001,
67000,1985,2040,1969,2024,1953,
67000,1937,1992,1921,1976,1905,
67000,1889,1944,1873,1928,1857,
67000,1841,1896,1825,1880,1809,
67000,1793,1848,1777,1832,1761,
67000,1745,1800,1729,1784,1713,
67000,1697,1752,1681,1736,1665,
67000,1649,1704,1633,1688,1617,
67000,1601,1656,1585,1640,1569,
67000,1553,1608,1537,1592,1521,
67000,1505,1560,1489,1544,1473,
67000,1457,1512,1441,1496,1425,
67000,1409,1464,1393,1448,1377,
67000,1361,1416,1345,1400,1329,
67000,1313,1368,1297,1352,1281,
67000,1265,1320,1249,1304,1233,
67000,1217,1272,1201,1256,1185,
67000,1169,1224,1153,1208,1137,
67000,1121,1176,1105,1160,1089,
67000,1073,1128,1057,1112,1041,
67000,1025,1080,1009,1064,993,
67000,977,1032,961,1016,945,
67000,929,984,913,968,897,
67000,881,936,865,920,849,
67000,833,888,817,872,801,
67000,785,840,769,824,753,
67000,737,792,721,776,705,
67000,689,744,673,728,657,
67000,641,696,625,680,609,
67000,593,648,577,632,561,
67000,545,600,529,584,513,
67000,497,552,481,536,465,
67000,449,504,433,488,417,
67000,401,456,385,440,369,
67000,353,408,337,392,321,
67000,305,360,289,344,273,
67000,257,312,241,296,225,
67000,209,264,193,248,177,
67000,161,216,145,200,129,
67000,113,168,97,152,81,
67000,65,120,49,104,33

[FireDelays]
25,[532,50]*7,532,[65257,25,[532,50]*7,532]*6

[ShellWhistleDelays]
219,[1139]*5,
270000,219,[2163]*5,
270000,219,[3187]*5,
270000,219,[4211]*5,
270000,219,[5235]*5,
270000,219,[6259]*5,
270000,219,[7283]*5