Spindash questions

So I drag'n'dropped the spindash code from the Nick Arcade Prototype (which, by the way, is unashamedly incomplete - there's a nop to indicate where further code was being implemented) and it worked straight off (all I did was comment it to make sure I understood what it was doing). However, I have some questions. First the code. (Feel free to use and abuse, since nothing here is actually mine.)

Code (Text):

1. ; ---------------------------------------------------------------------------
2. ; Subroutine to allow Sonic to spindash
3. ; ---------------------------------------------------------------------------
4.  
5. ; ||||||||||||||| S U B R O U T I N E |||||||||||||||||||||||||||||||||||||||
6.  
7. Sonic_Spindash:
8.         tst.b   $39(a0) ; are we charging a spindash?
9.         bne.s   Sonic_Spindashing; if so, go to the spindash charge code
10.         cmpi.b  #8,$1C(a0); are we using animation 8 (ducking)?
11.         bne.s   Sonic_NoSpindash; if not, don't do anything
12.         move.b  ($FFFFF603).w,d0; check currently held buttons
13.         andi.b  #$70,d0 ; are A, B or C pressed?
14.         beq.w   Sonic_NoSpindash; if not, don't do anything
15.         move.b  #9,$1C(a0); start using animation 9 (spindash, actually warp 1)
16.         move.w  #$BE,d0
17.         jsr (PlaySound_Special).l; play sound BE (spin sound)
18.         addq.l  #4,sp
19.         move.b  #1,$39(a0); set spindash charge flag
20.  
21. Sonic_NoSpindash:
22.         rts
23. ; ===========================================================================
24.  
25. Sonic_Spindashing:
26.         move.b  ($FFFFF602).w,d0
27.         btst    #1,d0   ; has down been released yet?
28.         bne.s   Sonic_ChargeSpindash; if not, go to charging code
29.         move.b  #$E,$16(a0); set height/2 to $E
30.         move.b  #7,$17(a0); set width/2 to $7
31.         move.b  #2,$1C(a0); use animation 2 (rolling)
32.         addq.w  #5,$C(a0); add 5 to upper byte of playfield Y coordinate (?)
33.         move.b  #0,$39(a0); unset spindash charge flag
34.         move.w  #$2000,($FFFFEED0).w; *
35.         move.w  #$800,$14(a0); set Sonic's speed to $800
36.         btst    #0,$22(a0); which way are we facing?
37.         beq.s   loc_103D4; if we're facing left, don't do anything
38.         neg.w   $14(a0) ; set speed in other direction if we're facing right
39.  
40. loc_103D4:
41.         bset    #2,$22(a0); set roll flag
42.         rts
43. ; ===========================================================================
44.  
45. Sonic_ChargeSpindash:
46.         move.b  ($FFFFF603).w,d0
47.         andi.b  #$70,d0 ; are A, B or C pressed?
48.         beq.w   Sonic_SkipCharging; if not, don't do anything
49.         nop     ; charging code is missing
50.  
51. Sonic_SkipCharging:
52.         addq.l  #4,sp
53.         rts
54. ; End of function Sonic_Spindash

Questions:
1) What is the purpose of the adding five to the playfield Y coordinate on line 32?
2) What is the purpose of moving $2000 into ($FFFFEED0).w on line 34? Does this have any bearing on question 3?
3) Why does the camera lock vertically when spindashing past the point at which the dynamic level resizing kicks in?

 

I have already tried that - it has no obvious effect. $EED0 is unreferenced elsewhere in the ROM.

I used the Nick Arcade spindash for its incompletion - what I plan on doing is far easier if I'm working with this unashamedly incomplete code compared to the complete code in S2F.

 

Ninja update:

I've done some more testing; it's not actually locking the Y position, but the Y position isn't changing fast enough and it can't keep up with Sonic's movement.

I'm going to assume this is a preventable problem since spindash was implemented correctly in Sonic 2, complete with pipes to run through; what do I need to do?

 

Ninja doublepost.

Stealth helped me realise where the problem is - the code for ducking is still being run, so the camera is being shifted down, which causes problems. Adding a delay identical to the one implemented in Sonic 2 final fixed the problem. (Now I know why they implemented that. :P)

Spindashing after that delay still causes problems at the moment, but I can deal with that fairly easily.