diff --git a/tools/bitmap editor/apple2_hires.md b/tools/bitmap editor/apple2_hires.md
index 2758dd7..6c55cbd 100644
--- a/tools/bitmap editor/apple2_hires.md	
+++ b/tools/bitmap editor/apple2_hires.md	
@@ -29,7 +29,7 @@ If we slightly modify the above code to POKE the first 3 lines as stored in memo
     30 FOR J = 0 TO 2
     40 FOR I = 0 TO 39
     50 POKE A, 255
-    60 A = A+ 1
+    60 A = A + 1
     70 NEXT I,J
     80 PRINT A
 
@@ -41,4 +41,51 @@ We have drawn line 0, line 64 and line 128 !
 Now the next address to `POKE` seems to be 8312 ($2078 in hex -- the resulting value in our variable `A`).
 
 But if we do `POKE 8312, 255` we don't see any change on the screen ! This is because we have reached one the hires screen holes !
+
 In fact, all lines between 128 and 191 in RAM have 8 unused bytes at their end. Those 8x64 lines represent 512 bytes. Those are the missing bytes in first computation.
+
+Now that we now that, we could slightly modify the above code so that after having drawn 3 lines, we add 8 to `A`so that it points to the next line location in memory. Let's do it and plot 3 times 3 lines.
+
+
+    10 HGR
+    20 A = 8192: REM $2000
+    30 FOR K = 0 TO 2
+    40 FOR J = 0 TO 2
+    50 FOR I = 0 TO 39
+    60 POKE A, 255
+    70 A = A + 1
+    80 NEXT I,J
+    90 A = A + 8
+    100 NEXT K
+    110 PRINT A
+
+We end up with
+
+![screenshot](img/apple2_hires_lines_triplets.png)
+
+As you watch how the lines are filled, you better understand the hires screen structure: 
+* the first 3 lines of 40 bytes delimit the three 64-lines sections and represent lines 0, 64 and 128 of the screen which are line 0 of each of the sections
+* then 8 bytes are wasted
+* the next 3 lines of 40 bytes represent line 8 of each of the 64 lines section (that is the base line of each section + 8, so we have lines 0+8, 64+8 and 128+8)
+* then 8 bytes are wasted
+* the next 3 lines of 40 bytes represent line 16 of each of the 64 lines section
+* the 8 bytes are wasted
+* This continues until we've arrived at line 56 relative to each section. That is line 56, line 64+56=120 and line 128+56=184.
+
+The following code will do it
+
+    10 HGR
+    20 A = 8192: REM $2000
+    30 FOR K = 0 TO 7
+    40 FOR J = 0 TO 2
+    50 FOR I = 0 TO 39
+    60 POKE A, 255
+    70 A = A + 1
+    80 NEXT I,J
+    90 A = A + 8
+    100 NEXT K
+    110 PRINT A
+
+![screenshot](img/apple2_hires_lines_8.png)
+
+So what happens next ?