[Tutorial] Title Screen Background Moveable in Sonic 1

[Mildanner]

So, you want to make a moveable title screen background for Sonic 1? Once the devs made it so known for having a famous moving right background, but what I do to move it?

It's simple, go to your disassembly root and in sonic.asm

You should find a label with the name "Tit_MainLoop:" and find this simple piece of code

        move.w    (v_player+obX).w,d0        ; get current title screen position (big Sonic object)
        addq.w    #2,d0                ; move it 2px to the right

Sounds simple? You can change the 2 with the number you want and changing the speed of it.

Replace it with this

        move.w    (v_objspace+obX).w,d0
        move.b    (v_jpadhold1).w,d1    ; Read pressed buttons

        ; --- Check B button to stop ---
        btst    #4,d1                ; Is B button held? (bit 4)
        bne.s    .ApplyMove           ; If yes, skip movement (stops Sonic)

        ; --- Speed Logic (Right) ---
        btst    #3,d1                ; Is Right held? (bit 3)
        bne.s    .FastRight           ; If yes, go to +4 speed
        addq.w    #2,d0                ; Default: +2 speed
        bra.s    .CheckLeft
.FastRight:
        addq.w    #4,d0                ; Fast: +4 speed

        ; --- Recoil Logic (Left) ---
.CheckLeft:
        btst    #2,d1                ; Is Left held? (bit 2)
        beq.s    .ApplyMove           ; If not, skip to applying movement
        subq.w    #4,d0                ; If yes, subtract 4 (move backward)

.ApplyMove:
        move.w    d0,(v_objspace+obX).w ; Save the new X position
        cmpi.w    #$1C00,d0            ; Check X-axis boundary limit
        blo.s    Tit_ChkRegion        ; If less than $1C00, branch to continue
.saveX:
        move.w    d0,(v_objspace+obX).w ; Update the X position

So, you can change the buttons to whatever you want.

Happy hacking!