Fix vertical scrolling controls

src/main.s

@@ -76,7 +76,19 @@ start:
 .update_up:
     ld hl, rSCY
     dec [hl]
+
+    ld a, [hl]
+    and %111
+    cp %111
+    jr nz, .update_up_map
+
+    ld a, [CURRENT_CAMERA_Y]
+    dec a
+    ld [CURRENT_CAMERA_Y], a
+
+.update_up_map:
     call Map_Scroll
+    jr .vbl
 
 .down:
     ld a, [keys]
@@ -98,7 +110,18 @@ start:
 .update_down:
     ld hl, rSCY
     inc [hl]
+
+    ld a, [hl]
+    and %111
+    jr nz, .update_down_map
+
+    ld a, [CURRENT_CAMERA_Y]
+    inc a
+    ld [CURRENT_CAMERA_Y], a
+
+.update_down_map:
     call Map_Scroll
+    jr .vbl
 
 .right:
     ld a, [keys]

src/map.s

@@ -111,69 +111,6 @@ Map_Load::
 
 ; Update map state based on SCX/SCY
 Map_Scroll::
-    ; Adjust CURRENT_CAMERA_X
-
-;     ; Adjust CURRENT_CAMERA_Y if [LAST_SCY]/8 != [rSCY]/8
-;     ld a, [rSCY]
-;     srl a
-;     srl a
-;     srl a
-
-;     ld hl, LAST_SCY
-;     ld b, [hl]
-;     srl b
-;     srl b
-;     srl b
-
-;     cp b
-;     jr c, .cmp
-;     jr z, .scroll_up_check
-
-;     sub $20
-
-; .cmp:
-;     sub b
-
-;     ld hl, CURRENT_CAMERA_Y
-;     add [hl]
-;     ld [hl], a
-
-    ; min([LAST_SCY]/8 - [SCY/8], [SCY/8] - [LAST_SCY]/8)
-
-    ld a, [LAST_SCY]
-    srl a
-    srl a
-    srl a
-    ld b, a
-
-    ld a, [rSCY]
-    srl a
-    srl a
-    srl a
-
-    ; c <- scy/8 - last_scy/8
-    sub b
-    ld c, a
-
-    ld a, [rSCY]
-    srl a
-    srl a
-    srl a
-    ld b, a
-
-    ld a, [LAST_SCY]
-    srl a
-    srl a
-    srl a
-    sub b
-    ; a <- last_scy/8 - scy/8
-
-    cp c
-
-.tryit:
-    ld [CURRENT_CAMERA_Y], a
-
-.scroll_up_check:
     ; If SCY = PAGEY, write map row
     ; map coords = CURRENT_CAMERA_X, CURRENT_CAMERA_Y - 2
     ; HL = _SCRN0 + 32 * (32 - page_y/8 - 2)