diff --git a/background.s b/background.s
index 7751683..f88d435 100644
--- a/background.s
+++ b/background.s
@@ -327,12 +327,23 @@ restorebg_cont lda (damageptr),y ; groups of 4 x1 -> x2, y1 -> y2
 
     ldy param_y
 restorebg_row lda textrows_h,y
+.if DEBUG_BOUNDS
+    cpy #24
+    bcc ?1
+    jsr debug_bounds
+.endif
+?1  lda textrows_h,y
     sta restorebg_row_smc+2
     lda textrows_l,y
     sta restorebg_row_smc+1
     ldx param_x
 restorebg_row_smc lda $ffff,x
-    jsr fastfont
+.if DEBUG_BOUNDS
+    cpx #40
+    bcc ?1
+    jsr debug_bounds
+.endif
+?1  jsr fastfont
     inx
     cpx param_col
     bcc restorebg_row_smc
diff --git a/debug.s b/debug.s
index 4e5a48c..22e9b37 100644
--- a/debug.s
+++ b/debug.s
@@ -45,6 +45,122 @@ printstr ; X = column, Y = row, scratch_ptr is text (null terminated)
     bne ?next
 ?exit rts
 
+error_bounds_text .byte "BOUNDS", 0
+
+; debug function to display address near where the problem was found.
+; By calling using a JSR, the return address is available on the stack
+error_bounds nop
+    lda #9
+    sta scratch_row
+
+    ldx #34 ; x coord on screen for "BOUNDS"
+    ldy scratch_row
+    lda #<error_bounds_text
+    sta scratch_ptr
+    lda #>error_bounds_text
+    sta scratch_ptr+1
+    jsr printstr
+
+    inc scratch_row
+    pla
+    ldx #38
+    ldy scratch_row
+    jsr debughex
+    pla
+    ldx #36
+    ldy scratch_row
+    jsr debughex
+
+    inc scratch_row
+    lda current_actor
+    ldx #38
+    ldy scratch_row
+    jsr debughex
+
+    inc scratch_row
+    ldx #34
+    ldy scratch_row
+    lda #'x'
+    jsr fastfont
+    ldx current_actor
+    lda actor_x,x
+    ldx #35
+    ldy scratch_row
+    jsr debughex
+    ldx current_actor
+    lda actor_y,x
+    ldx #38
+    ldy scratch_row
+    jsr debughex
+
+    inc scratch_row
+    ldx #34
+    ldy scratch_row
+    lda #'c'
+    jsr fastfont
+    ldx current_actor
+    lda actor_col,x
+    ldx #35
+    ldy scratch_row
+    jsr debughex
+    ldx current_actor
+    lda actor_row,x
+    ldx #38
+    ldy scratch_row
+    jsr debughex
+
+    inc scratch_row
+    ldx #34
+    ldy scratch_row
+    lda #'p'
+    jsr fastfont
+    ldx current_actor
+    lda actor_xpixel,x
+    ldx #35
+    ldy scratch_row
+    jsr debughex
+    ldx current_actor
+    lda actor_ypixel,x
+    ldx #38
+    ldy scratch_row
+    jsr debughex
+
+    inc scratch_row
+    ldx #34
+    ldy scratch_row
+    lda #'.'
+    jsr fastfont
+    ldx current_actor
+    lda actor_xfrac,x
+    ldx #35
+    ldy scratch_row
+    jsr debughex
+    ldx current_actor
+    lda actor_yfrac,x
+    ldx #38
+    ldy scratch_row
+    jsr debughex
+
+    inc scratch_row
+    ldx #34
+    ldy scratch_row
+    lda #'d'
+    jsr fastfont
+    ldx current_actor
+    lda actor_dir,x
+    ldx #35
+    ldy scratch_row
+    jsr debughex
+    ldx current_actor
+    lda actor_target_col,x
+    ldx #38
+    ldy scratch_row
+    jsr debughex
+
+    jsr pageflip
+    ldx current_actor ; restore X register
+?1  jmp ?1 ; wait for debugger
+
 
 debug_damage .byte 0
 debug_paint_box .byte 0
diff --git a/logic.s b/logic.s
index ffae821..871d1e6 100644
--- a/logic.s
+++ b/logic.s
@@ -56,13 +56,23 @@ evaluate_status nop
 ; convert tile and sub-tile position into coordinate on screen
 get_sprite nop
     lda actor_row,x
-    tay
+.if DEBUG_BOUNDS
+    cmp #24
+    bcc ?1
+    jsr debug_bounds
+.endif
+?1  tay
     lda player_row_to_y,y
     clc
     adc actor_ypixel,x
     sta actor_y,x
     lda actor_col,x
-    tay
+.if DEBUG_BOUNDS
+    cmp #40
+    bcc ?2
+    jsr debug_bounds
+.endif
+?2  tay
     lda player_col_to_x,y
     clc
     adc actor_xpixel,x
@@ -369,7 +379,13 @@ move_tile nop
 ?left lda actor_xpixel,x
     bpl ?right
     dec actor_col,x
-    lda actor_xpixel,x
+.if DEBUG_BOUNDS
+    lda actor_col,x
+    cmp #MAZE_LEFT_COL
+    bcs ?1b
+    jsr error_bounds
+.endif
+?1b lda actor_xpixel,x
     clc
     adc #X_TILEMAX
     sta actor_xpixel,x
@@ -382,7 +398,13 @@ move_tile nop
     cmp #X_TILEMAX
     bcc ?up
     inc actor_col,x
-    lda actor_xpixel,x
+.if DEBUG_BOUNDS
+    lda actor_col,x
+    cmp #MAZE_RIGHT_COL+1
+    bcc ?2b
+    jsr error_bounds
+.endif
+?2b lda actor_xpixel,x
     sec
     sbc #X_TILEMAX
     sta actor_xpixel,x
@@ -396,7 +418,13 @@ move_tile nop
 ?up lda actor_ypixel,x
     bpl ?down
     dec actor_row,x
-    lda actor_ypixel,x
+.if DEBUG_BOUNDS
+    lda actor_row,x
+    cmp #MAZE_TOP_ROW
+    bcs ?3b
+    jsr error_bounds
+.endif
+?3b lda actor_ypixel,x
     clc
     adc #Y_TILEMAX
     sta actor_ypixel,x
@@ -409,7 +437,13 @@ move_tile nop
     cmp #Y_TILEMAX
     bcc ?ret
     inc actor_row,x
-    lda actor_ypixel,x
+.if DEBUG_BOUNDS
+    lda actor_row,x
+    cmp #MAZE_BOT_ROW+1
+    bcc ?4b
+    jsr error_bounds
+.endif
+?4b lda actor_ypixel,x
     sec
     sbc #Y_TILEMAX
     sta actor_ypixel,x
diff --git a/main.s b/main.s
index ecc41f6..4ce192b 100644
--- a/main.s
+++ b/main.s
@@ -1,5 +1,10 @@
     *= $6000
 
+; conditional compilation flags
+
+DEBUG_BOUNDS = 1
+
+
 .include "macros.s"
 .include "constants.s"