Every time you press B, 0x80 is subtracted from Y subpixel speed. Otherwise, it either is nullified (on the ground), or just increases by 8 (in midair) each frame. Max Y speed is 3.0.
Every frame you hold direction, X subpixel speed increases by 16. Limit is 2.00.


They spawn with frame step of 46. Spawn slot depends on RNG which is rolled several times per frame while enemies or their eggs, or frag score is on-screen. So by picking eggs at different frames you can manipulate where the next enemy spawns.
However, in the first wave, they always spawn at the same spots: upper, upper and left slots.
Addresses $7C-$80 show which enemy occupies what spawn slot.


System: Nintendo Entertainment System
Domain Address Data Type Signed Endian Description
RAM 46 Byte Signed Big RNG1
RAM 47 Byte Signed Big RNG2
RAM 124 Byte Signed Big Spawn Slots
RAM 78 Byte Signed Big X Speed Offset
RAM 80 Byte Signed Big Y Speed Sub
RAM 82 Byte Signed Big Y Speed
RAM 84 Byte Signed Big X Pos
RAM 86 Byte Signed Big X Pos Sub
RAM 88 Byte Signed Big Y Pos
RAM 90 Byte Signed Big Y Pos Sub

-- NES Joust HUD
-- feos, 2014
function Joust()
	local rng    = memory.readbyte(0x2E)
	local x      = memory.readbyte(0x54)
	local xSub   = memory.readbyte(0x56) / 32
	local y      = memory.readbyte(0x58)
	local ySub   = memory.readbyte(0x5A) / 32
	local xSpeedOffset = memory.readbytesigned(0x4E)
	local xSpeed = memory.readbytesigned(0xCF69+xSpeedOffset) + memory.readbyte(0xCFAB+xSpeedOffset)/256
	local ySpeed = memory.readbytesigned(0x52) + memory.readbyte(0x50)/256
	local s1     = memory.readbyte(0x7C+0)
	local s2     = memory.readbyte(0x7C+1)
	local s3     = memory.readbyte(0x7C+2)
	local s4     = memory.readbyte(0x7C+3)
	local s5     = memory.readbyte(0x7C+4)
	local s6     = memory.readbyte(0x7C+5)
	gui.text(  1,224,string.format("\nSlots: %d %d %d %d %d %d",s1,s2,s3,s4,s5,s6))
	gui.text(110,224,string.format("\nRNG: %X",rng))
	gui.text(124,202,string.format("X: %.2f\nY: %.2f",xSpeed,ySpeed))
	gui.text(180,202,string.format("X: %3d.%d\nY: %3d.%d",x,xSub,y,ySub))
	RNGcount = 0

$D440 LDY #$03
$D442 ASL rng1
$D444 ROL rng2
$D446 ROL
$D447 ROL
$D448 EOR rng1
$D44B EOR rng1
$D44F EOR #$FF
$D451 AND #$01
$D453 ORA rng1
$D455 STA rng1
$D457 DEY
$D458 BPL $D442
$D45A RTS 

$EB32 LDA rng1
$EB34 AND #$03
$EB38 LDY $0032
$EB3C STA spawn slot,X

GameResources/NES/Joust last edited by admin@tasvideos.org 20 days ago
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