GameResources/NES/Joust

Positioning

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.

Enemies

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.

Details

BizHawk .wch file: UserFiles/Info/637936906484701185


-- 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
end
emu.registerafter(Joust)


$D440 LDY #$03
$D442 ASL rng1
$D444 ROL rng2
$D446 ROL
$D447 ROL
$D448 EOR rng1
$D44A ROL
$D44B EOR rng1
$D44D LSR
$D44E LSR
$D44F EOR #$FF
$D451 AND #$01
$D453 ORA rng1
$D455 STA rng1
$D457 DEY
$D458 BPL $D442
$D45A RTS


$EB2F JSR RNG Roll
$EB32 LDA rng1
$EB34 AND #$03
$EB36 BNE $EB3C
$EB38 LDY $0032
$EB3A BEQ $EB2F
$EB3C STA spawn slot,X

Positioning

Enemies

Details

See also