diff -Naurp 0verkill-0.16.old/data.c 0verkill-0.16/data.c
--- 0verkill-0.16.old/data.c	2007-10-30 19:49:59.000000000 +0100
+++ 0verkill-0.16/data.c	2007-10-30 20:25:08.000000000 +0100
@@ -471,7 +471,7 @@ my_double can_go_x(my_double old_x,my_do
 		for (x=double2int(old_x)+1;x<=round_up(new_x);x++)  /* go to the right */
 		{
 			if (x>AREA_X-1) return int2double(AREA_X-1);
-			for (y=yh;y<=yl;y++)
+			for (y=(yh>=0?yh:0);y<=yl;y++)
 				if ((area_a[x+y*AREA_X]&240)==TYPE_WALL)
 					return int2double(x-1);
 		}
@@ -479,7 +479,7 @@ my_double can_go_x(my_double old_x,my_do
 		for (x=round_up(old_x)-1;x>=double2int(new_x);x--)  /* go to the left */
 		{
 			if (x<0) return 0;
-			for (y=yh;y<=yl;y++)
+			for (y=(yh>=0?yh:0);y<=yl;y++)
 				if ((area_a[x+y*AREA_X]&240)==TYPE_WALL) return int2double(x+1);
 		}
 	if(flag)*flag=0;
@@ -501,7 +501,7 @@ my_double can_go_y(my_double old_y, my_d
 		for (y=double2int(old_y)+1;y<=round_up(new_y);y++)  /* go down */
 		{
 			if (y>AREA_Y-1) return int2double(AREA_Y-1);
-			for (x=xl;x<=xr;x++)
+			for (x=(xl>=0?xl:0);x<=xr;x++)
 				if ((area_a[x+y*AREA_X]&240)==TYPE_WALL||(!down_ladder&&((area_a[x+y*AREA_X]&240)==TYPE_JUMP||(area_a[x+y*AREA_X]&240)==TYPE_JUMP_FOREGROUND))) return int2double(y-1);
 		}
 	else
@@ -510,7 +510,7 @@ my_double can_go_y(my_double old_y, my_d
 		for (y=round_up(old_y)-1;y>=double2int(new_y);y--)  /* go up */
 		{
 			if (y<0) return 0;
-			for (x=xl;x<=xr;x++)
+			for (x=(xl>=0?xl:0);x<=xr;x++)
 				if ((area_a[x+y*AREA_X]&240)==TYPE_WALL) return int2double(y+1);
 		}
 	}