fix rare minimap corruption at edge of area

patches/rom_map/Bank 90.txt

@@ -7,4 +7,5 @@ F980 - F99E: ; respin.asm
 FC00 - FC0F: ; Fake Lava.asm
 FC10 - FC1C: ; crash_handle_yapping.asm
 FC20 - FC3A: ; remove_spikesuit.asm
-FC40 - FCBA: ; split_speed.asm
+FC40 - FCBA: ; split_speed.asm
+FD00 - FD40: ; map_progress_maintain.asm

patches/src/map_progress_maintain.asm

@@ -385,4 +385,40 @@ fix_mb:
     ldx #$0122
     rtl
 
-assert pc() <= !bank_a4_free_space_end
+assert pc() <= !bank_a4_free_space_end
+
+!bank_90_free_space_start = $90FD00
+!bank_90_free_space_end = $90FD40
+
+org $90aa29 ;;; jsr $ab75 (seam fix)
+  jsr minimapfix
+
+org !bank_90_free_space_start
+
+minimapfix:
+    lda $22
+    beq .page0
+    lda $2e
+    beq .right_edge     ; page 1, same byte -> right edge of map
+    bra .seam
+.page0:
+    lda $2e
+    bne .left_edge      ; page 0, origin in earlier byte -> left edge of map
+.seam:
+    jmp $ab75        
+
+.right_edge:            ; off-map tiles are in the low bytes
+    sep #$20
+    stz $18 : stz $1a : stz $1c
+    stz $26 : stz $28 : stz $2a
+    rep #$20
+    rts
+
+.left_edge:             ; off-map tiles are in the high bytes
+    sep #$20
+    stz $19 : stz $1b : stz $1d
+    stz $27 : stz $29 : stz $2b
+    rep #$20
+    rts
+
+assert pc() <= !bank_90_free_space_end