;small document about the beams' running code

$90AEF3
	
	LDA $0C04,x	;acceleration direction
	AND #$00F0	
	BEQ BRANCH_ALPHA ;branch if still "alive"
	JSR $90ADB7	;delete beam
	RTS

BRANCH_ALPHA:

	DEC $0C90,x	;timer for projectile trails
	BNE +
	LDA #$0004
	STA $0C90,x	;4 frames
	JSR $90B657	;trail movement/position
	LDX $0DDE	;current projectile index

+
	LDA $0C04,x	;accelerating direction
	AND #$000F
	ASL a
	TAY
	LDA $0BDC,x	;handles acceleration
	CLC
	ADC $C353,y	;this is loaded from ROM
	STA $0BDC,x
	LDA $0BF0,x
	CLC
	ADC $C367,y

	STA $0BF0,x
	TYX		;now X holds direction *2
	JSR ($AF36,x)	;execute code for indivitual movement directions
	JSR $B16A	;deletes beam if offscreen
	RTS

@ 90AF36:
	DW $AF4A	; U
	DW $AF52	; UR
	DW $AF60	; R
	DW $AF52	; DR
	DW $AF4A	; D
	DW $AF4A	; D
	DW $AF52	; DL
	DW $AF60	; L
	DW $AF52	; UL
	DW $AF4A	; U
	
@ 90B657:		;trail spawning routine?
{
	PHB		;push bank
	LDA $0C18,x	;projectile type
	BIT #$0F00
	BNE ALPHA	;branch if not a beam
	AND #$003F
	BRA BETA
ALPHA:
	XBA
	AND #$000F
	CMP #$0003
	BCS LEAVE	;leave if it's a bomb
	CLC
	ADC #$001F
BETA:
	ASL a
	TAX
	PEA $7E7E	;set bank to 7E (RAM)
	PLB
	PLB		;pull it into the Bank register
	LDY #$0022	;maximum of 18 trails onscreen
-
	LDA $D658,y	;find an empty spot in RAM
	BEQ GAMMA
	DEY
	DEY
	BPL -

LEAVE:
	PLB
	SEC		;set carry = no trail drawn
	RTL

GAMMA:
	LDA #$0001	
	STA $D658,y	;set flag for beam so this spot is used 
	STA $D67C,y	;timer
	LDA $90B5BB,x	;load special alignment?
	STA $D6A0,y
	LDA $90B609,x	;load type of trails?
	STA $D6C4,y
	LDX $0DDE
	JSR $9BA3CC	;finally draw the trail (not going to look into that >_>)
	PLB
	CLC		;we have successfully drawn a trail, so get us outta here
	RTL
}