Sonic 1 Prototype Code Snippet

*cd_walk            equ 0*2
*cd_jump            equ 1*2
*cd_up              equ 2*2
*cd_down            equ 3*2

updotmax        equ -4
downdotmax      equ 4
jumpdotmax      equ 8

;sprvo          equ $1c
;sprho          equ $1d
;sprvs          equ $1e
;sprhs          equ $1f
;------------------------------------------------------------------------
;   foot colition
;
;col:
    move.w  yposi(a0),d4
    move.b  sprvo(a0),d1
    add.b   sprvs(a0),d1
    ext.w   d1
    add.w   d1,d4
    move.w  xposi(a0),d5
    move.b  sprho(a0),d1
    ext.w   d1
    add.w   d1,d5
    move.w  xspeed(a0),scrhithz
?loop:
    move.w  d4,d2
    move.w  d5,d3
    moveq   #0,d0
    move.b  sprhs(a0),d0
    tst.w   xspeed(a0)
    bpl.b   ?jump
*   btst.b  #cd_right,cddot(a0)
*   beq.b   ?jump
    neg.w   d0
?jump:
    add.w   d0,d3
    bsr.w   scdchk
    tst.w   d1
    beq.b   ?end
    bpl.b   ?down
?up:
    cmp.w   #updotmax,d1
    blt.b   ?nomove
    add.w   d1,yposi(a0)
?end:
    rts
?nomove:
    bsr.b   hoseihsub
    bra.b   ?loop
    move.w  #0,xspeed(a0)
    rts
?down:
    move.w  d1,d6
    swap    d6
?down2:
    move.w  d4,d2
    move.w  d6,d3
    moveq   #0,d0
    move.b  sprhs(a0),d0
    tst.w   xspeed(a0)
    bpl.b   ?jump3
*   btst    #cd_left,cddot(a0)
*   bne.s   ?jump3
    neg.w   d0
?jump3:
    add.w   d0,d3
    bsr.w   scdchk
    tst.w   d1
    beq.b   ?end2
    bpl.b   ?down1
?up2:
    cmp.w   #updotmax,d1
    blt.b   ?nomove2