diff --git a/src/bus.rs b/src/bus.rs
index 5d00f3a..897e21c 100644
--- a/src/bus.rs
+++ b/src/bus.rs
@@ -46,7 +46,7 @@ impl Default for Bus {
 }
 
 impl Bus {
-    pub fn with_boot(path: &str) -> anyhow::Result<Self> {
+    pub(crate) fn with_boot(path: &str) -> anyhow::Result<Self> {
         let mut file = File::open(path)?;
         let mut boot_rom = [0u8; 256];
 
@@ -58,29 +58,29 @@ impl Bus {
         })
     }
 
-    pub fn load_cartridge(&mut self, path: &str) -> std::io::Result<()> {
+    pub(crate) fn load_cartridge(&mut self, path: &str) -> std::io::Result<()> {
         self.cartridge = Some(Cartridge::new(path)?);
         Ok(())
     }
 
-    pub fn rom_title(&self) -> Option<&str> {
+    pub(crate) fn rom_title(&self) -> Option<&str> {
         self.cartridge.as_ref()?.title()
     }
 
-    pub fn step(&mut self, cycles: Cycle) {
+    pub(crate) fn step(&mut self, cycles: Cycle) {
         self.step_dma(cycles);
         self.ppu.step(cycles);
         self.timer.step(cycles);
         self.sound.step(cycles);
     }
 
-    pub fn timer(&self) -> Timer {
+    pub(crate) fn timer(&self) -> Timer {
         self.timer
     }
 }
 
 impl Bus {
-    pub fn read_byte(&self, addr: u16) -> u8 {
+    pub(crate) fn read_byte(&self, addr: u16) -> u8 {
         match addr {
             0x0000..=0x3FFF => {
                 // 16KB ROM bank 00
@@ -193,7 +193,7 @@ impl Bus {
         }
     }
 
-    pub fn write_byte(&mut self, addr: u16, byte: u8) {
+    pub(crate) fn write_byte(&mut self, addr: u16, byte: u8) {
         match addr {
             0x0000..=0x3FFF => {
                 // 16KB ROM bank 00
@@ -323,11 +323,11 @@ impl Bus {
         }
     }
 
-    pub fn read_word(&self, addr: u16) -> u16 {
+    pub(crate) fn read_word(&self, addr: u16) -> u16 {
         (self.read_byte(addr + 1) as u16) << 8 | self.read_byte(addr) as u16
     }
 
-    pub fn write_word(&mut self, addr: u16, word: u16) {
+    pub(crate) fn write_word(&mut self, addr: u16, word: u16) {
         self.write_byte(addr + 1, (word >> 8) as u8);
         self.write_byte(addr, (word & 0x00FF) as u8);
     }
@@ -376,7 +376,7 @@ impl Bus {
         self.timer.set_interrupt(timer);
     }
 
-    pub fn boot_enabled(&self) -> bool {
+    pub(crate) fn boot_enabled(&self) -> bool {
         self.boot.is_some()
     }
 }
diff --git a/src/cartridge.rs b/src/cartridge.rs
index 8d05019..5e61ca8 100644
--- a/src/cartridge.rs
+++ b/src/cartridge.rs
@@ -7,14 +7,14 @@ const ROM_SIZE_ADDRESS: usize = 0x0148;
 const MBC_TYPE_ADDRESS: usize = 0x0147;
 
 #[derive(Debug, Clone, Default)]
-pub struct Cartridge {
+pub(crate) struct Cartridge {
     memory: Vec<u8>,
     title: Option<String>,
     mbc: Box<dyn MemoryBankController>,
 }
 
 impl Cartridge {
-    pub fn new<P: AsRef<Path> + ?Sized>(path: &P) -> io::Result<Self> {
+    pub(crate) fn new<P: AsRef<Path> + ?Sized>(path: &P) -> io::Result<Self> {
         let mut memory = vec![];
         let mut rom = File::open(path)?;
         rom.read_to_end(&mut memory)?;
@@ -59,7 +59,7 @@ impl Cartridge {
         str_with_nulls.map(|s| s.trim_matches('\0').to_string())
     }
 
-    pub fn title(&self) -> Option<&str> {
+    pub(crate) fn title(&self) -> Option<&str> {
         self.title.as_deref()
     }
 
@@ -87,7 +87,7 @@ impl Cartridge {
 }
 
 impl Cartridge {
-    pub fn read_byte(&self, addr: u16) -> u8 {
+    pub(crate) fn read_byte(&self, addr: u16) -> u8 {
         use MbcResult::*;
 
         match self.mbc.handle_read(addr) {
@@ -95,15 +95,15 @@ impl Cartridge {
             Value(byte) => byte,
         }
     }
-    pub fn write_byte(&mut self, addr: u16, byte: u8) {
+    pub(crate) fn write_byte(&mut self, addr: u16, byte: u8) {
         self.mbc.handle_write(addr, byte);
     }
 
-    pub fn read_word(&self, addr: u16) -> u16 {
+    pub(crate) fn read_word(&self, addr: u16) -> u16 {
         (self.read_byte(addr + 1) as u16) << 8 | self.read_byte(addr) as u16
     }
 
-    pub fn write_word(&mut self, addr: u16, word: u16) {
+    pub(crate) fn write_word(&mut self, addr: u16, word: u16) {
         self.write_byte(addr + 1, (word >> 8) as u8);
         self.write_byte(addr, (word & 0x00FF) as u8);
     }
@@ -294,7 +294,7 @@ enum RamSize {
 }
 
 impl RamSize {
-    pub fn as_byte_count(&self) -> u32 {
+    pub(crate) fn as_byte_count(&self) -> u32 {
         use RamSize::*;
 
         match *self {
@@ -354,7 +354,7 @@ impl Default for BankCount {
 
 impl BankCount {
     // https://hacktix.github.io/GBEDG/mbcs/#rom-size
-    pub fn to_byte_count(self) -> u32 {
+    pub(crate) fn to_byte_count(self) -> u32 {
         use BankCount::*;
 
         match self {
diff --git a/src/cpu.rs b/src/cpu.rs
index afce18f..e77f044 100644
--- a/src/cpu.rs
+++ b/src/cpu.rs
@@ -42,15 +42,15 @@ impl Cpu {
         })
     }
 
-    pub fn ime(&self) -> ImeState {
+    pub(crate) fn ime(&self) -> ImeState {
         self.ime
     }
 
-    pub fn set_ime(&mut self, state: ImeState) {
+    pub(crate) fn set_ime(&mut self, state: ImeState) {
         self.ime = state;
     }
 
-    pub fn halt(&mut self, state: HaltState) {
+    pub(crate) fn halt(&mut self, state: HaltState) {
         self.halted = Some(state);
     }
 
@@ -58,11 +58,11 @@ impl Cpu {
         self.halted = None;
     }
 
-    pub fn halted(&self) -> Option<HaltState> {
+    pub(crate) fn halted(&self) -> Option<HaltState> {
         self.halted
     }
 
-    pub fn inc_pc(&mut self) {
+    pub(crate) fn inc_pc(&mut self) {
         self.reg.pc += 1;
     }
 
@@ -76,15 +76,15 @@ impl Cpu {
 }
 
 impl Cpu {
-    pub fn fetch(&self) -> u8 {
+    pub(crate) fn fetch(&self) -> u8 {
         self.bus.read_byte(self.reg.pc)
     }
 
-    pub fn decode(&mut self, opcode: u8) -> Instruction {
+    pub(crate) fn decode(&mut self, opcode: u8) -> Instruction {
         Instruction::from_byte(self, opcode)
     }
 
-    pub fn execute(&mut self, instruction: Instruction) -> Cycle {
+    pub(crate) fn execute(&mut self, instruction: Instruction) -> Cycle {
         Instruction::execute(self, instruction)
     }
 
@@ -128,30 +128,30 @@ impl Cpu {
 }
 
 impl Cpu {
-    pub fn read_imm_byte(&mut self, addr: u16) -> u8 {
+    pub(crate) fn read_imm_byte(&mut self, addr: u16) -> u8 {
         self.inc_pc(); // NB: the addr read in the line below will be equal to PC - 1 after this function call
         self.bus.read_byte(addr)
     }
 
-    pub fn read_imm_word(&mut self, addr: u16) -> u16 {
+    pub(crate) fn read_imm_word(&mut self, addr: u16) -> u16 {
         self.inc_pc();
         self.inc_pc(); // NB: the addr read in the line below will be equal to PC - 2 after this function call
         self.bus.read_word(addr)
     }
 
-    pub fn read_byte(&self, addr: u16) -> u8 {
+    pub(crate) fn read_byte(&self, addr: u16) -> u8 {
         self.bus.read_byte(addr)
     }
 
-    pub fn write_byte(&mut self, addr: u16, byte: u8) {
+    pub(crate) fn write_byte(&mut self, addr: u16, byte: u8) {
         self.bus.write_byte(addr, byte);
     }
 
-    pub fn read_word(&mut self, addr: u16) -> u16 {
+    pub(crate) fn read_word(&mut self, addr: u16) -> u16 {
         self.bus.read_word(addr)
     }
 
-    pub fn write_word(&mut self, addr: u16, word: u16) {
+    pub(crate) fn write_word(&mut self, addr: u16, word: u16) {
         self.bus.write_word(addr, word)
     }
 }
@@ -260,7 +260,7 @@ impl Default for State {
 }
 
 impl Cpu {
-    pub fn set_register(&mut self, register: Register, value: u8) {
+    pub(crate) fn set_register(&mut self, register: Register, value: u8) {
         use Register::*;
 
         match register {
@@ -275,7 +275,7 @@ impl Cpu {
         }
     }
 
-    pub fn register(&self, register: Register) -> u8 {
+    pub(crate) fn register(&self, register: Register) -> u8 {
         use Register::*;
 
         match register {
@@ -290,7 +290,7 @@ impl Cpu {
         }
     }
 
-    pub fn register_pair(&self, pair: RegisterPair) -> u16 {
+    pub(crate) fn register_pair(&self, pair: RegisterPair) -> u16 {
         use RegisterPair::*;
 
         match pair {
@@ -303,7 +303,7 @@ impl Cpu {
         }
     }
 
-    pub fn set_register_pair(&mut self, pair: RegisterPair, value: u16) {
+    pub(crate) fn set_register_pair(&mut self, pair: RegisterPair, value: u16) {
         use RegisterPair::*;
 
         let high = (value >> 8) as u8;
@@ -331,17 +331,17 @@ impl Cpu {
         }
     }
 
-    pub fn flags(&self) -> &Flags {
+    pub(crate) fn flags(&self) -> &Flags {
         &self.flags
     }
 
-    pub fn set_flags(&mut self, flags: Flags) {
+    pub(crate) fn set_flags(&mut self, flags: Flags) {
         self.flags = flags;
     }
 }
 
 impl Cpu {
-    pub fn log_state(&self, mut writer: impl std::io::Write) -> std::io::Result<()> {
+    pub(crate) fn log_state(&self, mut writer: impl std::io::Write) -> std::io::Result<()> {
         write!(writer, "A: {:02X} ", self.reg.a)?;
         write!(writer, "F: {:02X} ", u8::from(self.flags))?;
         write!(writer, "B: {:02X} ", self.reg.b)?;
@@ -363,7 +363,7 @@ impl Cpu {
 }
 
 #[derive(Debug, Copy, Clone)]
-pub enum Register {
+pub(crate) enum Register {
     A,
     B,
     C,
@@ -375,7 +375,7 @@ pub enum Register {
 }
 
 #[derive(Debug, Copy, Clone)]
-pub enum RegisterPair {
+pub(crate) enum RegisterPair {
     AF,
     BC,
     DE,
@@ -407,7 +407,7 @@ bitfield! {
 }
 
 impl Flags {
-    pub fn update(&mut self, z: bool, n: bool, h: bool, c: bool) {
+    pub(crate) fn update(&mut self, z: bool, n: bool, h: bool, c: bool) {
         self.set_z(z);
         self.set_n(n);
         self.set_h(h);
@@ -469,14 +469,14 @@ impl From<u8> for Flags {
 }
 
 #[derive(Debug, Clone, Copy)]
-pub enum HaltState {
+pub(crate) enum HaltState {
     ImeEnabled,
     NonePending,
     SomePending,
 }
 
 #[derive(Debug, Clone, Copy)]
-pub enum ImeState {
+pub(crate) enum ImeState {
     Disabled,
     Pending,
     PendingEnd,
diff --git a/src/gui.rs b/src/gui.rs
index a1c2033..7e31d91 100644
--- a/src/gui.rs
+++ b/src/gui.rs
@@ -19,7 +19,7 @@ pub struct Egui {
     render_pass: RenderPass,
     paint_jobs: Vec<ClippedMesh>,
 
-    pub config: Configuration,
+    pub(crate) config: Configuration,
 
     show_flags: bool,
     show_cpu_info: bool,
@@ -30,7 +30,7 @@ pub struct Egui {
     #[cfg(feature = "debug")]
     show_disasm: bool,
     #[cfg(feature = "debug")]
-    pub break_point: Option<u16>,
+    pub(crate) break_point: Option<u16>,
 }
 
 impl Egui {
@@ -367,14 +367,14 @@ impl Egui {
     }
 }
 
-pub struct Configuration {
+pub(crate) struct Configuration {
     /// Show Configuration egui menu
     show: bool,
 
     /// How many [`LR35902`] .step() do we want to do at once
     /// when pressing the spacebar key?
     #[cfg(feature = "debug")]
-    pub spacebar_step: u16,
+    pub(crate) spacebar_step: u16,
 }
 
 impl Default for Configuration {
diff --git a/src/high_ram.rs b/src/high_ram.rs
index b10e9f9..2e62a05 100644
--- a/src/high_ram.rs
+++ b/src/high_ram.rs
@@ -2,7 +2,7 @@ const HIGH_RAM_SIZE: usize = 0x7F;
 const HIGH_RAM_START_ADDRESS: usize = 0xFF80;
 
 #[derive(Debug, Clone)]
-pub struct HighRam {
+pub(crate) struct HighRam {
     buf: Box<[u8; HIGH_RAM_SIZE]>,
 }
 
@@ -15,11 +15,11 @@ impl Default for HighRam {
 }
 
 impl HighRam {
-    pub fn write_byte(&mut self, addr: u16, byte: u8) {
+    pub(crate) fn write_byte(&mut self, addr: u16, byte: u8) {
         self.buf[addr as usize - HIGH_RAM_START_ADDRESS] = byte;
     }
 
-    pub fn read_byte(&self, addr: u16) -> u8 {
+    pub(crate) fn read_byte(&self, addr: u16) -> u8 {
         self.buf[addr as usize - HIGH_RAM_START_ADDRESS]
     }
 }
diff --git a/src/instruction.rs b/src/instruction.rs
index 63d85bf..34f9a08 100644
--- a/src/instruction.rs
+++ b/src/instruction.rs
@@ -3,7 +3,7 @@ use std::{convert::TryFrom, fmt::Debug};
 
 #[derive(Copy, Clone)]
 #[allow(clippy::upper_case_acronyms)]
-pub enum Instruction {
+pub(crate) enum Instruction {
     NOP,
     LD(LDTarget, LDTarget),
     STOP,
@@ -51,26 +51,26 @@ pub enum Instruction {
 }
 
 #[derive(Copy, Clone)]
-pub enum JPTarget {
+pub(crate) enum JPTarget {
     RegisterPair(RegisterPair),
     ImmediateWord(u16),
 }
 
 #[derive(Copy, Clone)]
-pub enum Registers {
+pub(crate) enum Registers {
     Byte(InstrRegister),
     Word(RegisterPair),
 }
 
 #[derive(Copy, Clone)]
-pub enum MATHTarget {
+pub(crate) enum MATHTarget {
     Register(InstrRegister),
     RegisterPair(RegisterPair),
     ImmediateByte(u8),
 }
 
 #[derive(Copy, Clone)]
-pub enum LDTarget {
+pub(crate) enum LDTarget {
     IndirectC,
     Register(InstrRegister),
     IndirectRegister(InstrRegisterPair),
@@ -82,7 +82,7 @@ pub enum LDTarget {
 }
 
 #[derive(Copy, Clone)]
-pub enum InstrRegisterPair {
+pub(crate) enum InstrRegisterPair {
     AF,
     BC,
     DE,
@@ -94,7 +94,7 @@ pub enum InstrRegisterPair {
 }
 
 #[derive(Copy, Clone)]
-pub enum InstrRegister {
+pub(crate) enum InstrRegister {
     A,
     B,
     C,
@@ -106,7 +106,7 @@ pub enum InstrRegister {
 }
 
 #[derive(Copy, Clone)]
-pub enum JumpCondition {
+pub(crate) enum JumpCondition {
     NotZero,
     Zero,
     NotCarry,
@@ -122,7 +122,7 @@ struct Table;
 pub struct Cycle(u32);
 
 impl Instruction {
-    pub fn execute(cpu: &mut Cpu, instruction: Self) -> Cycle {
+    pub(crate) fn execute(cpu: &mut Cpu, instruction: Self) -> Cycle {
         match instruction {
             Instruction::NOP => Cycle::new(4),
             Instruction::LD(lhs, rhs) => match (lhs, rhs) {
@@ -1608,7 +1608,7 @@ impl Instruction {
         (lower << 4) | upper
     }
 
-    pub fn reset(cpu: &mut Cpu, vector: u8) -> Cycle {
+    pub(crate) fn reset(cpu: &mut Cpu, vector: u8) -> Cycle {
         let addr = cpu.register_pair(RegisterPair::PC);
         Self::push(cpu, addr);
         cpu.set_register_pair(RegisterPair::PC, vector as u16);
@@ -1617,7 +1617,7 @@ impl Instruction {
 }
 
 impl Instruction {
-    pub fn from_byte(cpu: &mut Cpu, byte: u8) -> Self {
+    pub(crate) fn from_byte(cpu: &mut Cpu, byte: u8) -> Self {
         if byte == 0xCB {
             Self::from_prefixed_byte(cpu)
         } else {
@@ -1911,7 +1911,7 @@ impl TryFrom<InstrRegister> for Register {
 }
 
 impl Table {
-    pub fn r(index: u8) -> InstrRegister {
+    pub(crate) fn r(index: u8) -> InstrRegister {
         match index {
             0 => InstrRegister::B,
             1 => InstrRegister::C,
@@ -1925,7 +1925,7 @@ impl Table {
         }
     }
 
-    pub fn rp2(index: u8) -> RegisterPair {
+    pub(crate) fn rp2(index: u8) -> RegisterPair {
         match index {
             0 => RegisterPair::BC,
             1 => RegisterPair::DE,
@@ -1935,7 +1935,7 @@ impl Table {
         }
     }
 
-    pub fn rp(index: u8) -> RegisterPair {
+    pub(crate) fn rp(index: u8) -> RegisterPair {
         match index {
             0 => RegisterPair::BC,
             1 => RegisterPair::DE,
@@ -1945,7 +1945,7 @@ impl Table {
         }
     }
 
-    pub fn cc(index: u8) -> JumpCondition {
+    pub(crate) fn cc(index: u8) -> JumpCondition {
         match index {
             0 => JumpCondition::NotZero,
             1 => JumpCondition::Zero,
@@ -1955,7 +1955,7 @@ impl Table {
         }
     }
 
-    pub fn x2_alu(index: u8, r_index: u8) -> Instruction {
+    pub(crate) fn x2_alu(index: u8, r_index: u8) -> Instruction {
         match index {
             0 => Instruction::ADD(
                 // ADD A, r[z]
@@ -1973,7 +1973,7 @@ impl Table {
         }
     }
 
-    pub fn x3_alu(index: u8, n: u8) -> Instruction {
+    pub(crate) fn x3_alu(index: u8, n: u8) -> Instruction {
         match index {
             0 => Instruction::ADD(
                 // ADD A, n
@@ -1991,7 +1991,7 @@ impl Table {
         }
     }
 
-    pub fn rot(index: u8, r_index: u8) -> Instruction {
+    pub(crate) fn rot(index: u8, r_index: u8) -> Instruction {
         match index {
             0 => Instruction::RLC(Self::r(r_index)),  // RLC r[z]
             1 => Instruction::RRC(Self::r(r_index)),  // RRC r[z]
@@ -2275,13 +2275,13 @@ impl From<Cycle> for u32 {
 }
 
 impl InstrRegisterPair {
-    pub fn to_register_pair(self) -> RegisterPair {
+    pub(crate) fn to_register_pair(self) -> RegisterPair {
         RegisterPair::try_from(self).expect("Failed to convert InstrRegisterPair to RegisterPair")
     }
 }
 
 impl InstrRegister {
-    pub fn to_register(self) -> Register {
+    pub(crate) fn to_register(self) -> Register {
         Register::try_from(self).expect("Failed to convert from InstrRegister to Register")
     }
 }
diff --git a/src/interrupt.rs b/src/interrupt.rs
index 9e2f706..7015965 100644
--- a/src/interrupt.rs
+++ b/src/interrupt.rs
@@ -1,19 +1,19 @@
 use bitfield::bitfield;
 
 #[derive(Debug, Clone, Copy, Default)]
-pub struct Interrupt {
-    pub flag: InterruptFlag,
-    pub enable: InterruptEnable,
+pub(crate) struct Interrupt {
+    pub(crate) flag: InterruptFlag,
+    pub(crate) enable: InterruptEnable,
 }
 
 bitfield! {
-    pub struct InterruptEnable(u8);
+   pub struct InterruptEnable(u8);
     impl Debug;
-    pub vblank, set_vblank: 0;
-    pub lcd_stat, set_lcd_stat: 1;
-    pub timer, set_timer: 2;
-    pub serial, set_serial: 3;
-    pub joypad, set_joypad: 4;
+   pub vblank, set_vblank: 0;
+   pub lcd_stat, set_lcd_stat: 1;
+   pub timer, set_timer: 2;
+   pub serial, set_serial: 3;
+   pub joypad, set_joypad: 4;
 }
 
 impl Copy for InterruptEnable {}
diff --git a/src/joypad.rs b/src/joypad.rs
index bd6dc6c..09e6dbb 100644
--- a/src/joypad.rs
+++ b/src/joypad.rs
@@ -7,11 +7,11 @@ pub struct Joypad {
 }
 
 impl Joypad {
-    pub fn interrupt(&self) -> bool {
+    pub(crate) fn interrupt(&self) -> bool {
         self.interrupt
     }
 
-    pub fn set_interrupt(&mut self, value: bool) {
+    pub(crate) fn set_interrupt(&mut self, value: bool) {
         self.interrupt = value;
     }
 }
diff --git a/src/ppu.rs b/src/ppu.rs
index 6e7934a..8b665e8 100644
--- a/src/ppu.rs
+++ b/src/ppu.rs
@@ -4,7 +4,7 @@ use crate::GB_WIDTH;
 use dma::DmaProcess;
 use std::collections::VecDeque;
 use std::convert::TryInto;
-pub use types::PpuMode;
+pub(crate) use types::PpuMode;
 use types::{
     BackgroundPalette, GrayShade, LCDControl, LCDStatus, ObjectFlags, ObjectPalette,
     ObjectPaletteId, ObjectSize, Pixels, RenderPriority, TileDataAddress,
@@ -34,13 +34,13 @@ const BLACK: [u8; 4] = 0x202020FFu32.to_be_bytes();
 
 #[derive(Debug, Clone)]
 pub struct Ppu {
-    pub int: Interrupt,
-    pub control: LCDControl,
-    pub monochrome: Monochrome,
-    pub pos: ScreenPosition,
-    pub vram: Box<[u8; VRAM_SIZE]>,
-    pub stat: LCDStatus,
-    pub oam: ObjectAttributeTable,
+    pub(crate) int: Interrupt,
+    pub(crate) control: LCDControl,
+    pub(crate) monochrome: Monochrome,
+    pub(crate) pos: ScreenPosition,
+    pub(crate) vram: Box<[u8; VRAM_SIZE]>,
+    pub(crate) stat: LCDStatus,
+    pub(crate) oam: ObjectAttributeTable,
     pub(crate) dma: DmaProcess,
     scan_state: OamScanState,
     fetch: PixelFetcher,
@@ -53,17 +53,17 @@ pub struct Ppu {
 }
 
 impl Ppu {
-    pub fn read_byte(&self, addr: u16) -> u8 {
+    pub(crate) fn read_byte(&self, addr: u16) -> u8 {
         self.vram[addr as usize - PPU_START_ADDRESS]
     }
 
-    pub fn write_byte(&mut self, addr: u16, byte: u8) {
+    pub(crate) fn write_byte(&mut self, addr: u16, byte: u8) {
         self.vram[addr as usize - PPU_START_ADDRESS] = byte;
     }
 }
 
 impl Ppu {
-    pub fn step(&mut self, cycles: Cycle) {
+    pub(crate) fn step(&mut self, cycles: Cycle) {
         let start: u32 = self.cycle.into();
         let end: u32 = cycles.into();
 
@@ -459,63 +459,63 @@ impl Default for Ppu {
 }
 
 #[derive(Debug, Clone, Copy, Default)]
-pub struct Interrupt {
+pub(crate) struct Interrupt {
     _vblank: bool,
     _lcd_stat: bool,
 }
 
 impl Interrupt {
-    pub fn vblank(&self) -> bool {
+    pub(crate) fn vblank(&self) -> bool {
         self._vblank
     }
 
-    pub fn set_vblank(&mut self, enabled: bool) {
+    pub(crate) fn set_vblank(&mut self, enabled: bool) {
         self._vblank = enabled;
     }
 
-    pub fn lcd_stat(&self) -> bool {
+    pub(crate) fn lcd_stat(&self) -> bool {
         self._lcd_stat
     }
 
-    pub fn set_lcd_stat(&mut self, enabled: bool) {
+    pub(crate) fn set_lcd_stat(&mut self, enabled: bool) {
         self._lcd_stat = enabled;
     }
 }
 
 #[derive(Debug, Clone, Copy, Default)]
-pub struct ScreenPosition {
-    pub scroll_y: u8,
-    pub scroll_x: u8,
-    pub line_y: u8,
-    pub ly_compare: u8,
-    pub window_y: u8,
-    pub window_x: u8,
+pub(crate) struct ScreenPosition {
+    pub(crate) scroll_y: u8,
+    pub(crate) scroll_x: u8,
+    pub(crate) line_y: u8,
+    pub(crate) ly_compare: u8,
+    pub(crate) window_y: u8,
+    pub(crate) window_x: u8,
 }
 
 #[derive(Debug, Clone, Copy, Default)]
-pub struct Monochrome {
-    pub bg_palette: BackgroundPalette,
-    pub obj_palette_0: ObjectPalette,
-    pub obj_palette_1: ObjectPalette,
+pub(crate) struct Monochrome {
+    pub(crate) bg_palette: BackgroundPalette,
+    pub(crate) obj_palette_0: ObjectPalette,
+    pub(crate) obj_palette_1: ObjectPalette,
 }
 
 #[derive(Debug, Clone)]
-pub struct ObjectAttributeTable {
+pub(crate) struct ObjectAttributeTable {
     buf: Box<[u8; OAM_SIZE]>,
 }
 
 impl ObjectAttributeTable {
-    pub fn read_byte(&self, addr: u16) -> u8 {
+    pub(crate) fn read_byte(&self, addr: u16) -> u8 {
         let index = (addr - 0xFE00) as usize;
         self.buf[index]
     }
 
-    pub fn write_byte(&mut self, addr: u16, byte: u8) {
+    pub(crate) fn write_byte(&mut self, addr: u16, byte: u8) {
         let index = (addr - 0xFE00) as usize;
         self.buf[index] = byte;
     }
 
-    pub fn attribute(&self, index: usize) -> ObjectAttribute {
+    pub(crate) fn attribute(&self, index: usize) -> ObjectAttribute {
         let start = index * 4;
 
         let slice: &[u8; 4] = self.buf[start..(start + 4)]
@@ -535,7 +535,7 @@ impl Default for ObjectAttributeTable {
 }
 
 #[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
-pub struct ObjectAttribute {
+pub(crate) struct ObjectAttribute {
     y: u8,
     x: u8,
     tile_index: u8,
@@ -571,7 +571,7 @@ struct ObjectBuffer {
 }
 
 impl ObjectBuffer {
-    pub fn iter(&self) -> std::slice::Iter<'_, Option<ObjectAttribute>> {
+    pub(crate) fn iter(&self) -> std::slice::Iter<'_, Option<ObjectAttribute>> {
         self.into_iter()
     }
 }
@@ -597,21 +597,21 @@ impl<'a> IntoIterator for &'a mut ObjectBuffer {
 }
 
 impl ObjectBuffer {
-    pub fn is_full(&self) -> bool {
+    pub(crate) fn is_full(&self) -> bool {
         self.len == OBJECT_LIMIT
     }
 
-    pub fn clear(&mut self) {
+    pub(crate) fn clear(&mut self) {
         self.buf = [Default::default(); 10];
         self.len = 0;
     }
 
-    pub fn add(&mut self, attr: ObjectAttribute) {
+    pub(crate) fn add(&mut self, attr: ObjectAttribute) {
         self.buf[self.len] = Some(attr);
         self.len += 1;
     }
 
-    pub fn remove(&mut self, attr: &ObjectAttribute) {
+    pub(crate) fn remove(&mut self, attr: &ObjectAttribute) {
         let maybe_index = self.buf.iter().position(|maybe_attr| match maybe_attr {
             Some(other_attr) => attr == other_attr,
             None => false,
@@ -640,13 +640,13 @@ struct PixelFetcher {
 }
 
 impl PixelFetcher {
-    pub fn hblank_reset(&mut self) {
+    pub(crate) fn hblank_reset(&mut self) {
         self.back.hblank_reset();
         self.obj.hblank_reset();
         self.x_pos = 0;
     }
 
-    pub fn vblank_reset(&mut self) {
+    pub(crate) fn vblank_reset(&mut self) {
         self.back.vblank_reset();
     }
 
@@ -716,7 +716,11 @@ impl PixelFetcher {
         }
     }
 
-    pub fn get_obj_addr(attr: &ObjectAttribute, pos: &ScreenPosition, size: ObjectSize) -> u16 {
+    pub(crate) fn get_obj_addr(
+        attr: &ObjectAttribute,
+        pos: &ScreenPosition,
+        size: ObjectSize,
+    ) -> u16 {
         let line_y = pos.line_y;
 
         // TODO: Why is the offset 14 and 30 respectively?
@@ -837,21 +841,21 @@ struct WindowLineCounter {
 }
 
 impl WindowLineCounter {
-    pub fn increment(&mut self) {
+    pub(crate) fn increment(&mut self) {
         self.count += 1;
     }
 
-    pub fn vblank_reset(&mut self) {
+    pub(crate) fn vblank_reset(&mut self) {
         self.count = 0;
     }
 
-    pub fn count(&self) -> u8 {
+    pub(crate) fn count(&self) -> u8 {
         self.count
     }
 }
 
 #[derive(Debug, Clone, Copy)]
-pub enum FetcherState {
+pub(crate) enum FetcherState {
     TileNumber,
     ToLowByteSleep,
     TileLowByte,
@@ -890,15 +894,15 @@ struct FifoRenderer {
 }
 
 impl FifoRenderer {
-    pub fn is_enabled(&self) -> bool {
+    pub(crate) fn is_enabled(&self) -> bool {
         self.enabled
     }
 
-    pub fn pause(&mut self) {
+    pub(crate) fn pause(&mut self) {
         self.enabled = false;
     }
 
-    pub fn resume(&mut self) {
+    pub(crate) fn resume(&mut self) {
         self.enabled = true;
     }
 }
@@ -921,19 +925,19 @@ struct TileBuilder {
 }
 
 impl TileBuilder {
-    pub fn with_id(&mut self, id: u8) {
+    pub(crate) fn with_id(&mut self, id: u8) {
         self.id = Some(id);
     }
 
-    pub fn with_low_byte(&mut self, data: u8) {
+    pub(crate) fn with_low_byte(&mut self, data: u8) {
         self.low = Some(data);
     }
 
-    pub fn with_high_byte(&mut self, data: u8) {
+    pub(crate) fn with_high_byte(&mut self, data: u8) {
         self.high = Some(data);
     }
 
-    pub fn bytes(&self) -> Option<(u8, u8)> {
+    pub(crate) fn bytes(&self) -> Option<(u8, u8)> {
         self.high.zip(self.low)
     }
 }
@@ -945,25 +949,25 @@ struct OamScanState {
 }
 
 impl OamScanState {
-    pub fn increase(&mut self) {
+    pub(crate) fn increase(&mut self) {
         self.count += 1;
         self.count %= 40;
     }
 
-    pub fn reset(&mut self) {
+    pub(crate) fn reset(&mut self) {
         self.count = Default::default();
         self.mode = Default::default();
     }
 
-    pub fn count(&self) -> u8 {
+    pub(crate) fn count(&self) -> u8 {
         self.count
     }
 
-    pub fn mode(&self) -> OamScanMode {
+    pub(crate) fn mode(&self) -> OamScanMode {
         self.mode
     }
 
-    pub fn next(&mut self) {
+    pub(crate) fn next(&mut self) {
         use OamScanMode::*;
 
         self.mode = match self.mode {
@@ -995,19 +999,19 @@ struct WindowStatus {
 }
 
 impl WindowStatus {
-    pub fn should_draw(&self) -> bool {
+    pub(crate) fn should_draw(&self) -> bool {
         self.should_draw
     }
 
-    pub fn coincidence(&self) -> bool {
+    pub(crate) fn coincidence(&self) -> bool {
         self.coincidence
     }
 
-    pub fn set_should_draw(&mut self, value: bool) {
+    pub(crate) fn set_should_draw(&mut self, value: bool) {
         self.should_draw = value;
     }
 
-    pub fn set_coincidence(&mut self, value: bool) {
+    pub(crate) fn set_coincidence(&mut self, value: bool) {
         self.coincidence = value;
     }
 
diff --git a/src/ppu/dma.rs b/src/ppu/dma.rs
index c119c9c..2dfdd40 100644
--- a/src/ppu/dma.rs
+++ b/src/ppu/dma.rs
@@ -88,7 +88,7 @@ impl Default for DmaControl {
 }
 
 impl DmaControl {
-    pub fn update(&mut self, byte: u8, state: &mut DmaState) {
+    pub(crate) fn update(&mut self, byte: u8, state: &mut DmaState) {
         let left = (byte as u16) << 8 | 0x0000;
         let right = (byte as u16) << 8 | 0x009F;
 
diff --git a/src/ppu/types.rs b/src/ppu/types.rs
index 0831065..de41f2d 100644
--- a/src/ppu/types.rs
+++ b/src/ppu/types.rs
@@ -14,7 +14,7 @@ bitfield! {
 }
 
 impl LCDStatus {
-    pub fn update(&mut self, byte: u8) {
+    pub(crate) fn update(&mut self, byte: u8) {
         // Bytes 2 -> 0 are read only
         let mask = 0b00000111;
 
@@ -119,7 +119,7 @@ pub enum TileMapAddress {
 }
 
 impl TileMapAddress {
-    pub fn into_address(self) -> u16 {
+    pub(crate) fn into_address(self) -> u16 {
         match self {
             TileMapAddress::X9800 => 0x9800,
             TileMapAddress::X9C00 => 0x9C00,
@@ -184,7 +184,7 @@ pub enum ObjectSize {
 }
 
 impl ObjectSize {
-    pub fn as_u8(&self) -> u8 {
+    pub(crate) fn as_u8(&self) -> u8 {
         use ObjectSize::*;
 
         match self {
@@ -226,7 +226,7 @@ bitfield! {
 }
 
 impl BackgroundPalette {
-    pub fn shade(&self, id: u8) -> GrayShade {
+    pub(crate) fn shade(&self, id: u8) -> GrayShade {
         match id & 0b11 {
             0b00 => self.i0_colour(),
             0b01 => self.i1_colour(),
@@ -271,7 +271,7 @@ bitfield! {
 }
 
 impl ObjectPalette {
-    pub fn shade(&self, id: u8) -> Option<GrayShade> {
+    pub(crate) fn shade(&self, id: u8) -> Option<GrayShade> {
         match id & 0b11 {
             0b00 => None,
             0b01 => Some(self.i1_colour()),
@@ -307,16 +307,16 @@ impl From<ObjectPalette> for u8 {
     }
 }
 
-pub struct Pixels(u8, u8);
+pub(crate) struct Pixels(u8, u8);
 
 impl Pixels {
-    pub const PIXEL_COUNT: usize = 8;
+    pub(crate) const PIXEL_COUNT: usize = 8;
 
-    pub fn from_bytes(higher: u8, lower: u8) -> Self {
+    pub(crate) fn from_bytes(higher: u8, lower: u8) -> Self {
         Self(higher, lower)
     }
 
-    pub fn shade_id(&self, x: usize) -> u8 {
+    pub(crate) fn shade_id(&self, x: usize) -> u8 {
         let bit = 7 - x;
 
         let higher = self.0 >> bit;
@@ -427,7 +427,7 @@ pub enum GrayShade {
 }
 
 impl GrayShade {
-    pub fn into_rgba(self) -> [u8; 4] {
+    pub(crate) fn into_rgba(self) -> [u8; 4] {
         match self {
             GrayShade::White => WHITE,
             GrayShade::LightGray => LIGHT_GRAY,
@@ -436,7 +436,7 @@ impl GrayShade {
         }
     }
 
-    pub fn from_rgba(slice: &[u8]) -> Self {
+    pub(crate) fn from_rgba(slice: &[u8]) -> Self {
         let rgba: [u8; 4] = slice
             .try_into()
             .expect("Unable to interpret &[u8] as [u8; 4]");
diff --git a/src/serial.rs b/src/serial.rs
index 4fba589..2907469 100644
--- a/src/serial.rs
+++ b/src/serial.rs
@@ -1,9 +1,9 @@
 use bitfield::bitfield;
 
 #[derive(Debug, Clone, Copy, Default)]
-pub struct Serial {
-    pub next: u8,
-    pub control: SerialControl,
+pub(crate) struct Serial {
+    pub(crate) next: u8,
+    pub(crate) control: SerialControl,
 }
 
 bitfield! {
diff --git a/src/sound.rs b/src/sound.rs
index eea5d17..024f323 100644
--- a/src/sound.rs
+++ b/src/sound.rs
@@ -1,22 +1,22 @@
 use crate::instruction::Cycle;
 use bitfield::bitfield;
 #[derive(Debug, Clone, Copy, Default)]
-pub struct Sound {
-    pub control: SoundControl,
-    pub ch1: Channel1,
+pub(crate) struct Sound {
+    pub(crate) control: SoundControl,
+    pub(crate) ch1: Channel1,
 }
 
 impl Sound {
-    pub fn step(&mut self, _cycles: Cycle) {
+    pub(crate) fn step(&mut self, _cycles: Cycle) {
         //
     }
 }
 
 #[derive(Debug, Clone, Copy, Default)]
-pub struct SoundControl {
-    pub channel: ChannelControl,
-    pub output: SoundOutput,
-    pub status: SoundStatus,
+pub(crate) struct SoundControl {
+    pub(crate) channel: ChannelControl,
+    pub(crate) output: SoundOutput,
+    pub(crate) status: SoundStatus,
 }
 
 // TODO: What to do about the separation of freq bits
@@ -79,7 +79,7 @@ impl From<u8> for FrequencyLow {
     }
 }
 
-pub fn get_11bit_freq(low: &FrequencyLow, high: FrequencyHigh) -> u16 {
+pub(crate) fn get_11bit_freq(low: &FrequencyLow, high: FrequencyHigh) -> u16 {
     let high_bits = high.0 & 0b111;
 
     (low.0 as u16) << 8 | ((high_bits as u16) << 4)
@@ -143,11 +143,11 @@ impl From<SoundStatus> for u8 {
 }
 
 #[derive(Debug, Clone, Copy, Default)]
-pub struct Channel1 {
-    pub sound_duty: SoundDuty,
-    pub vol_envelope: VolumeEnvelope,
-    pub freq_hi: FrequencyHigh,
-    pub freq_lo: FrequencyLow,
+pub(crate) struct Channel1 {
+    pub(crate) sound_duty: SoundDuty,
+    pub(crate) vol_envelope: VolumeEnvelope,
+    pub(crate) freq_hi: FrequencyHigh,
+    pub(crate) freq_lo: FrequencyLow,
 }
 
 bitfield! {
@@ -206,10 +206,10 @@ impl Default for EnvelopeDirection {
 }
 
 bitfield! {
-    pub struct SoundDuty(u8);
+   pub struct SoundDuty(u8);
     impl Debug;
-    pub from into WavePattern, wave_pattern, set_wave_pattern: 7, 6;
-    pub _, set_sound_length: 5, 0; // TODO: Getter only used if bit 6 in NR14 is set
+   pub from into WavePattern, wave_pattern, set_wave_pattern: 7, 6;
+   pub _, set_sound_length: 5, 0; // TODO: Getter only used if bit 6 in NR14 is set
 }
 
 impl Copy for SoundDuty {}
diff --git a/src/timer.rs b/src/timer.rs
index 971c753..6e889d7 100644
--- a/src/timer.rs
+++ b/src/timer.rs
@@ -2,17 +2,17 @@ use crate::Cycle;
 use bitfield::bitfield;
 
 #[derive(Debug, Clone, Copy)]
-pub struct Timer {
-    pub control: TimerControl,
-    pub counter: u8,
-    pub modulo: u8,
-    pub divider: u16,
+pub(crate) struct Timer {
+    pub(crate) control: TimerControl,
+    pub(crate) counter: u8,
+    pub(crate) modulo: u8,
+    pub(crate) divider: u16,
     prev_and_result: Option<u8>,
     interrupt: bool,
 }
 
 impl Timer {
-    pub fn step(&mut self, cycles: Cycle) {
+    pub(crate) fn step(&mut self, cycles: Cycle) {
         use TimerSpeed::*;
 
         for _ in 0..cycles.into() {
@@ -52,11 +52,11 @@ impl Timer {
         }
     }
 
-    pub fn interrupt(&self) -> bool {
+    pub(crate) fn interrupt(&self) -> bool {
         self.interrupt
     }
 
-    pub fn set_interrupt(&mut self, value: bool) {
+    pub(crate) fn set_interrupt(&mut self, value: bool) {
         self.interrupt = value;
     }
 }
diff --git a/src/work_ram.rs b/src/work_ram.rs
index 852bbbc..6654807 100644
--- a/src/work_ram.rs
+++ b/src/work_ram.rs
@@ -4,16 +4,16 @@ const WORK_RAM_START_ADDRESS: usize = 0xC000;
 const VARIABLE_WORK_RAM_START_ADDRESS: usize = 0xD000;
 
 #[derive(Debug, Clone)]
-pub struct WorkRam {
+pub(crate) struct WorkRam {
     bank: Box<[u8; WORK_RAM_SIZE]>,
 }
 
 impl WorkRam {
-    pub fn write_byte(&mut self, addr: u16, byte: u8) {
+    pub(crate) fn write_byte(&mut self, addr: u16, byte: u8) {
         self.bank[addr as usize - WORK_RAM_START_ADDRESS] = byte;
     }
 
-    pub fn read_byte(&self, addr: u16) -> u8 {
+    pub(crate) fn read_byte(&self, addr: u16) -> u8 {
         self.bank[addr as usize - WORK_RAM_START_ADDRESS]
     }
 }
@@ -27,7 +27,7 @@ impl Default for WorkRam {
 }
 
 #[derive(Debug, Clone, Copy)]
-pub enum BankNumber {
+pub(crate) enum BankNumber {
     One = 1,
     Two = 2,
     Three = 3,
@@ -38,7 +38,7 @@ pub enum BankNumber {
 }
 
 #[derive(Debug, Clone)]
-pub struct VariableWorkRam {
+pub(crate) struct VariableWorkRam {
     current: BankNumber,
     bank_n: Box<[[u8; VARIABLE_WORK_RAM_SIZE]; 7]>, // 4K for Variable amount of Banks (Banks 1 -> 7) in Game Boy Colour
 }
@@ -53,19 +53,19 @@ impl Default for VariableWorkRam {
 }
 
 impl VariableWorkRam {
-    pub fn set_current_bank(&mut self, bank: BankNumber) {
+    pub(crate) fn set_current_bank(&mut self, bank: BankNumber) {
         self.current = bank;
     }
 
-    pub fn get_current_bank(&self) -> BankNumber {
+    pub(crate) fn get_current_bank(&self) -> BankNumber {
         self.current
     }
 
-    pub fn write_byte(&mut self, addr: u16, byte: u8) {
+    pub(crate) fn write_byte(&mut self, addr: u16, byte: u8) {
         self.bank_n[self.current as usize][addr as usize - VARIABLE_WORK_RAM_START_ADDRESS] = byte;
     }
 
-    pub fn read_byte(&self, addr: u16) -> u8 {
+    pub(crate) fn read_byte(&self, addr: u16) -> u8 {
         self.bank_n[self.current as usize][addr as usize - VARIABLE_WORK_RAM_START_ADDRESS]
     }
 }