; ---------------------------------------------------------------------------
; Subroutine to make Sonic perform a spindash
; ---------------------------------------------------------------------------

; ||||||||||||||| S U B	R O U T	I N E |||||||||||||||||||||||||||||||||||||||


Sonic_SpinDash:
		tst.b	$39(a0)				; already Spin Dashing?
		bne.s	Spindash_CheckRelease		; if set, branch
		cmpi.b	#8,$1C(a0)			; is anim duck
		bne.s	Spindash_Return			; if not, return
		move.b	($FFFFF603).w,d0		; read controller
		andi.b	#$70,d0				; pressing A/B/C ?
		beq.s	Spindash_Return			; if not, return
		move.b	#9,$1C(a0)			; set Spin Dash anim (9 in s2)
		move.w	#$D1,d0				; spin sound ($E0 in s2)
		jsr	(PlaySound_Special).l		; play spin sound
		addq.l	#4,sp				; increment stack ptr
		move.b	#1,$39(a0)			; set Spin Dash flag
		move.b	#0,$3A(a0)			; set charge count to 0
		cmpi.b	#$C,$28(a0)			; ??? oxygen remaining?
		bcs.s	Spindash_CallNecessaryRoutines	; ??? branch if carry
		move.b	#2,($FFFFD11C).w		; ??? $D11C is used for
							; the smoke/dust object
Spindash_CallNecessaryRoutines:
		bsr.w	Sonic_LevelBoundaries
		bsr.w	Sonic_AnglePos

Spindash_Return:
		rts
; ---------------------------------------------------------------------------

Spindash_CheckRelease:
;		move.b	#9,$1C(a0)
		move.b	($FFFFF602).w,d0		; read controller
		btst	#1,d0				; check down button
		bne.w	Spindash_StillCharging		; if set, branch
		move.b	#$E,$16(a0)			; $16(a0) is height/2
		move.b	#7,$17(a0)			; $17(a0) is width/2
		move.b	#2,$1C(a0)			; set animation to roll
		addq.w	#5,$C(a0)			; $C(a0) is Y coordinate
		move.b	#0,$39(a0)			; clear Spin Dash flag
		moveq	#0,d0
		move.b	$3A(a0),d0			; copy charge count
		add.w	d0,d0				; double it
		move.w	Dash_Speeds(pc,d0.w),$14(a0) 	; get normal speed
		move.w	$14(a0),d0			; get inertia
		subi.w	#$800,d0			; subtract $800
		add.w	d0,d0				; double it
		andi.w	#$1F00,d0			; mask it against $1F00
		neg.w	d0				; negate it
		addi.w	#$2000,d0			; add $2000
		move.w	d0,($FFFFEED0).w		; move to $EED0
		btst	#0,$22(a0)			; is sonic facing right?
		beq.s	Spindash_Release2		; if not, branch
		neg.w	$14(a0)				; negate inertia

Spindash_Release2:
		bset	#2,$22(a0)			; set rolling flag
		move.b	#0,($FFFFD11C).w		; clear $D11C (smoke)
		move.w	#$BC,d0				; spin release sound
		jsr	(PlaySound_Special).l		; play it!

		move.b	angle(a0),d0			; Load Sonic's angle to d0.
		jsr	(CalcSine).l			; Calculate Sonic's sine and cosine based on his angle.
		muls.w	inertia(a0),d1			; Multiply d1 by Sonic's inertia.
		asr.l	#8,d1				; Divide the longword in d1 by 2*2*2*2*2*2*2*2 = 256 (also read as 2^8 = 256).
		move.w	d1,x_vel(a0)			; Give Sonic horizontal velocity. This has no effect when Sonic is on flat ground at a 0- or 180-degree angle.
		muls.w	inertia(a0),d0			; Multiply d0 by Sonic's inertia.
		asr.l	#8,d0				; Divide the longword in d0 by 2*2*2*2*2*2*2*2 = 256 (also read as 2^8 = 256).
		move.w	d0,y_vel(a0)			; Give Sonic vertical velocity. This has no effect when Sonic is on flat ground that is at a 90- or 270-degree angle.

		bra.s	Spindash_ResetScr
; ===========================================================================
Dash_Speeds:
		dc.w  $800		; 0
		dc.w  $880		; 1
		dc.w  $900		; 2
		dc.w  $980		; 3
		dc.w  $A00		; 4
		dc.w  $A80		; 5
		dc.w  $B00		; 6
		dc.w  $B80		; 7
		dc.w  $C00		; 8
; ===========================================================================

Spindash_StillCharging:					; If still charging the dash...
		tst.b	$3A(a0)				; check charge count
		beq.s	Spindash_Recharge		; if zero, branch
		move.b	$3A(a0),d0			; otherwise put it in d0
		lsr.b	#5,d0				; shift right 5 (divide it by 32)
		sub.b	d0,$3A(a0)			; subtract from charge count
		bcc.s	Spindash_Recharge		; ??? branch if carry clear
		move.b	#0,$3A(a0)			; set charge count to 0

Spindash_Recharge:
		move.b	($FFFFF603).w,d0		; read controller
		andi.b	#$70,d0				; pressing A/B/C?
		beq.w	Spindash_ResetScr		; if not, branch
		move.w	#$900,$1C(a0)			; reset spdsh animation
		move.w	#$D1,d0				; was $E0 in sonic 2
		jsr	(PlaySound_Special).l		; play charge sound
		addi.b	#$1,spindash_counter(a0)
		cmpi.b	#$8,spindash_counter(a0)
		bcs.s	Spindash_ResetScr
		move.b	#$8,spindash_counter(a0)
		bra.s	Spindash_ResetScr
		move.b	#$8,spindash_counter(a0)

Spindash_ResetScr:
		addq.l	#4,sp				; increase stack ptr
		cmpi.w	#$60,($FFFFEED8).w		; $EED8 only ever seems
		beq.s	Spindash_CallNecessaryRoutines2	; to be used in Spin Dash
		bcc.s	Spindash_ResetScr_Part2
		addq.w	#4,($FFFFEED8).w

Spindash_ResetScr_Part2:
		subq.w	#2,($FFFFEED8).w

Spindash_CallNecessaryRoutines2:
		bsr.w	Sonic_LevelBoundaries
		bsr.w	Sonic_AnglePos
;		move.w	#$60,($FFFFF73E).w		; reset looking up/down
		rts
; End of subroutine Sonic_SpinDash
; ===========================================================================
		align 4