diff --git a/book/src-bak/SUMMARY.md b/book/src-bak/SUMMARY.md
new file mode 100644
index 0000000..a177f06
--- /dev/null
+++ b/book/src-bak/SUMMARY.md
@@ -0,0 +1,23 @@
+
+# Rust GBA Tutorials
+
+* [Introduction](introduction.md)
+* [Ch 0: Development Setup](ch00/index.md)
+* [Ch 1: Hello GBA](ch01/index.md)
+  * [hello1](ch01/hello1.md)
+  * [Volatile](ch01/volatile.md)
+  * [IO Registers](ch01/io_registers.md)
+  * [The Display Control Register](ch01/the_display_control_register.md)
+  * [Video Memory Intro](ch01/video_memory_intro.md)
+  * [hello2](ch01/hello2.md)
+* [Ch 2: User Input](ch02/index.md)
+  * [The Key Input Register](ch02/the_key_input_register.md)
+  * [The VCount Register](ch02/the_vcount_register.md)
+  * [light_cycle](ch02/light_cycle.md)
+* [Ch 3: Memory and Objects](ch03/index.md)
+  * [GBA Memory Mapping](ch03/gba_memory_mapping.md)
+  * [Tile Data](ch03/tile_data.md)
+  * [Regular Backgrounds](ch03/regular_backgrounds.md)
+  * [Regular Objects](ch03/regular_objects.md)
+  * [GBA PRNG](ch03/gba_prng.md)
+  * [memory_game](ch03/memory_game.md)
diff --git a/book/src/ch00/index.md b/book/src-bak/ch00/index.md
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diff --git a/book/src/ch01/hello1.md b/book/src-bak/ch01/hello1.md
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diff --git a/book/src/ch01/io_registers.md b/book/src-bak/ch01/io_registers.md
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diff --git a/book/src/ch01/the_display_control_register.md b/book/src-bak/ch01/the_display_control_register.md
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diff --git a/book/src/ch01/video_memory_intro.md b/book/src-bak/ch01/video_memory_intro.md
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diff --git a/book/src/ch01/volatile.md b/book/src-bak/ch01/volatile.md
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diff --git a/book/src/ch02/index.md b/book/src-bak/ch02/index.md
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diff --git a/book/src/ch02/light_cycle.md b/book/src-bak/ch02/light_cycle.md
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diff --git a/book/src/ch02/the_key_input_register.md b/book/src-bak/ch02/the_key_input_register.md
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diff --git a/book/src/ch02/the_vcount_register.md b/book/src-bak/ch02/the_vcount_register.md
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diff --git a/book/src/ch03/gba_memory_mapping.md b/book/src-bak/ch03/gba_memory_mapping.md
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rename from book/src/ch03/gba_memory_mapping.md
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diff --git a/book/src/ch03/gba_prng.md b/book/src-bak/ch03/gba_prng.md
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diff --git a/book/src/ch03/index.md b/book/src-bak/ch03/index.md
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diff --git a/book/src/ch03/memory_game.md b/book/src-bak/ch03/memory_game.md
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index 0bb11af..3e65170 100644
--- a/book/src/ch03/memory_game.md
+++ b/book/src-bak/ch03/memory_game.md
@@ -183,7 +183,7 @@ pub struct RegularScreenblockEntry(u16);
 
 impl RegularScreenblockEntry {
   pub const SCREENBLOCK_ENTRY_TILE_ID_MASK: u16 = 0b11_1111_1111;
-  pub fn from_tile_id(id: u16) -> Self {
+  pub const fn from_tile_id(id: u16) -> Self {
     RegularScreenblockEntry(id & Self::SCREENBLOCK_ENTRY_TILE_ID_MASK)
   }
 }
@@ -243,8 +243,9 @@ the "screen base block" value.
 pub struct BackgroundControlSetting(u16);
 
 impl BackgroundControlSetting {
-  pub fn from_base_block(sbb: u16) -> Self {
-    BackgroundControlSetting(sbb << 8)
+  pub const SCREEN_BASE_BLOCK_MASK: u16 = 0b1_1111;
+  pub const fn from_base_block(sbb: u16) -> Self {
+    BackgroundControlSetting((sbb & Self::SCREEN_BASE_BLOCK_MASK) << 8)
   }
 }
 
diff --git a/book/src/ch03/obj_memory_2d1d.jpg b/book/src-bak/ch03/obj_memory_2d1d.jpg
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diff --git a/book/src/ch03/regular_backgrounds.md b/book/src-bak/ch03/regular_backgrounds.md
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rename from book/src/ch03/regular_backgrounds.md
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diff --git a/book/src/ch03/regular_objects.md b/book/src-bak/ch03/regular_objects.md
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rename from book/src/ch03/regular_objects.md
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diff --git a/book/src/ch03/screenshot_checkers.png b/book/src-bak/ch03/screenshot_checkers.png
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rename from book/src/ch03/screenshot_checkers.png
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diff --git a/book/src/ch03/tile_data.md b/book/src-bak/ch03/tile_data.md
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diff --git a/book/src/introduction.md b/book/src-bak/introduction.md
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diff --git a/book/src/SUMMARY.md b/book/src/SUMMARY.md
index a177f06..1847cab 100644
--- a/book/src/SUMMARY.md
+++ b/book/src/SUMMARY.md
@@ -1,23 +1,34 @@
 
-# Rust GBA Tutorials
-
-* [Introduction](introduction.md)
-* [Ch 0: Development Setup](ch00/index.md)
-* [Ch 1: Hello GBA](ch01/index.md)
-  * [hello1](ch01/hello1.md)
-  * [Volatile](ch01/volatile.md)
-  * [IO Registers](ch01/io_registers.md)
-  * [The Display Control Register](ch01/the_display_control_register.md)
-  * [Video Memory Intro](ch01/video_memory_intro.md)
-  * [hello2](ch01/hello2.md)
-* [Ch 2: User Input](ch02/index.md)
-  * [The Key Input Register](ch02/the_key_input_register.md)
-  * [The VCount Register](ch02/the_vcount_register.md)
-  * [light_cycle](ch02/light_cycle.md)
-* [Ch 3: Memory and Objects](ch03/index.md)
-  * [GBA Memory Mapping](ch03/gba_memory_mapping.md)
-  * [Tile Data](ch03/tile_data.md)
-  * [Regular Backgrounds](ch03/regular_backgrounds.md)
-  * [Regular Objects](ch03/regular_objects.md)
-  * [GBA PRNG](ch03/gba_prng.md)
-  * [memory_game](ch03/memory_game.md)
+* Introduction
+  * Goals Of This Book
+  * Prerequisites
+  * Getting Outside Help
+  * Development Setup
+  * Hello Magic
+  * Volatile
+  * Core Only
+* Broad Concepts
+  * BIOS
+  * Working RAM
+  * IO Registers
+  * Palette RAM
+  * Video RAM
+  * Object Attribute Memory
+  * Game Pak ROM / Flash ROM
+  * Save RAM
+* Video Modes
+  * RBG15 Color
+  * Bitmap Modes
+  * Tiled Modes
+  * Affine Math
+  * Special Effects
+* Non-Video Hardware
+  * Buttons
+  * Timers
+  * Direct Memory Access
+  * Sound
+  * Interrupts
+  * Network
+  * Game Pak
+* Examples
+  * for example in example_list
diff --git a/examples/memory_game.rs b/examples/memory_game.rs
index 9ccb037..c18a00c 100644
--- a/examples/memory_game.rs
+++ b/examples/memory_game.rs
@@ -107,7 +107,7 @@ pub struct RegularScreenblockEntry(u16);
 
 impl RegularScreenblockEntry {
   pub const SCREENBLOCK_ENTRY_TILE_ID_MASK: u16 = 0b11_1111_1111;
-  pub fn from_tile_id(id: u16) -> Self {
+  pub const fn from_tile_id(id: u16) -> Self {
     RegularScreenblockEntry(id & Self::SCREENBLOCK_ENTRY_TILE_ID_MASK)
   }
 }
@@ -136,8 +136,9 @@ pub fn checker_screenblock(slot: usize, a_entry: RegularScreenblockEntry, b_entr
 pub struct BackgroundControlSetting(u16);
 
 impl BackgroundControlSetting {
-  pub fn from_base_block(sbb: u16) -> Self {
-    BackgroundControlSetting(sbb << 8)
+  pub const SCREEN_BASE_BLOCK_MASK: u16 = 0b1_1111;
+  pub const fn from_base_block(sbb: u16) -> Self {
+    BackgroundControlSetting((sbb & Self::SCREEN_BASE_BLOCK_MASK) << 8)
   }
 }