38 files changed, 335 insertions, 228 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5bfbf5d..abd4f29 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -4,11 +4,49 @@ project(
     LANGUAGES CXX OBJCXX OBJC
     VERSION 1.0)
 
-set(CMAKE_CXX_STANDARD 17)
+option(NES_ENABLE_SANITIZER_ADDRESS "Enable address sanitizer." OFF)
+option(NES_ENABLE_SANITIZER_UNDEFINED_BEHAVIOR "Enable undefined behavior sanitizer." OFF)
+option(NES_ENABLE_DEBUG_OUTPUT "Enable debug output." OFF)
+option(NES_ENABLE_PPU "Enable Picture Processing Unit." ON)
 
-add_executable(nes)
-add_subdirectory(src)
+add_library(nes_options INTERFACE)
+add_library(nes::options ALIAS nes_options)
+target_compile_features(nes_options INTERFACE cxx_std_17)
+target_compile_options(nes_options
+    INTERFACE
+        -Wall
+        -Wextra
+        -Wnon-virtual-dtor
+        -Wcast-align
+        -Wunused
+        -Woverloaded-virtual
+        -Wpedantic
+        -Wconversion
+        -Wsign-conversion
+        -Wdouble-promotion
+        -Wformat=2
+        -Wswitch-enum
+        -Wno-gnu-anonymous-struct)
+if(APPLE)
+    # Use automatic reference counting for Objective-C code.
+    target_compile_options(nes_options INTERFACE "-fobjc-arc")
+endif()
+if(NES_ENABLE_SANITIZER_ADDRESS AND NES_ENABLE_SANITIZER_UNDEFINED_BEHAVIOR)
+    message(FATAL_ERROR "Address sanitizer and undefined behavior sanitizer cannot be enabled at the same time.")
+elseif(NES_ENABLE_SANITIZER_ADDRESS)
+    target_compile_options(nes_options INTERFACE -fsanitize=address)
+elseif(NES_ENABLE_SANITIZER_UNDEFINED_BEHAVIOR)
+    target_compile_options(nes_options INTERFACE -fsanitize=undefined)
+endif()
 
-find_library(FRAMEWORK_COCOA Cocoa REQUIRED)
-find_library(FRAMEWORK_SPRITEKIT SpriteKit REQUIRED)
-target_link_libraries(nes PRIVATE ${FRAMEWORK_COCOA} ${FRAMEWORK_SPRITEKIT})
\ No newline at end of file
+if(NES_ENABLE_DEBUG_OUTPUT)
+    include(FetchContent)
+    FetchContent_Declare(
+        spdlog
+        GIT_REPOSITORY https://github.com/gabime/spdlog.git
+        GIT_TAG v1.15.0)
+    FetchContent_MakeAvailable(spdlog)
+endif()
+
+add_subdirectory(lib)
+add_subdirectory(app)
\ No newline at end of file
diff --git a/app/CMakeLists.txt b/app/CMakeLists.txt
new file mode 100644
index 0000000..8ff9434
--- /dev/null
+++ b/app/CMakeLists.txt
@@ -0,0 +1,5 @@
+if(APPLE)
+	add_subdirectory(mac)
+endif()
+
+add_subdirectory(test)
\ No newline at end of file
diff --git a/app/mac/CMakeLists.txt b/app/mac/CMakeLists.txt
new file mode 100644
index 0000000..a4f25c9
--- /dev/null
+++ b/app/mac/CMakeLists.txt
@@ -0,0 +1,20 @@
+add_executable(nes_mac)
+
+find_library(FRAMEWORK_COCOA Cocoa REQUIRED)
+find_library(FRAMEWORK_SPRITEKIT SpriteKit REQUIRED)
+
+target_include_directories(nes_mac PRIVATE .)
+target_link_libraries(
+	nes_mac
+	PRIVATE
+		nes::options
+		nes::nes
+		${FRAMEWORK_COCOA}
+		${FRAMEWORK_SPRITEKIT})
+
+target_sources(
+	nes_mac
+	PRIVATE
+		main.mm
+		scene.hh
+		scene.mm)
\ No newline at end of file
diff --git a/src/main.mm b/app/mac/main.mm
index 5ca7c5c..5ca7c5c 100644
--- a/src/main.mm
+++ b/app/mac/main.mm
diff --git a/src/scene.hh b/app/mac/scene.hh
index 1660e66..1660e66 100644
--- a/src/scene.hh
+++ b/app/mac/scene.hh
diff --git a/src/scene.mm b/app/mac/scene.mm
index f858185..f858185 100644
--- a/src/scene.mm
+++ b/app/mac/scene.mm
diff --git a/app/test/CMakeLists.txt b/app/test/CMakeLists.txt
new file mode 100644
index 0000000..b88acc2
--- /dev/null
+++ b/app/test/CMakeLists.txt
@@ -0,0 +1,14 @@
+add_executable(nes_test)
+
+target_include_directories(nes_test PRIVATE .)
+target_link_libraries(
+	nes_test
+	PRIVATE
+		nes::options
+		nes::nes
+		nes::ref)
+
+target_sources(
+	nes_test
+	PRIVATE
+		main.cc)
\ No newline at end of file
diff --git a/app/test/main.cc b/app/test/main.cc
new file mode 100644
index 0000000..3bb785f
--- /dev/null
+++ b/app/test/main.cc
@@ -0,0 +1,76 @@
+#include "nes/display.hh"
+#include "nes/nes.hh"
+#include "nes/util/rgb.hh"
+#include "nes/util/snapshot.hh"
+#include <iostream>
+
+namespace
+{
+	class dummy_display final : public nes::display
+	{
+		std::uint8_t buffer_a_[width * height * 3]{};
+		std::uint8_t buffer_b_[width * height * 3]{};
+		std::uint8_t* front_buffer_{ buffer_a_ };
+		std::uint8_t* back_buffer_{ buffer_b_ };
+
+	public:
+		explicit dummy_display() = default;
+
+		auto get(unsigned const x, unsigned const y) const -> nes::rgb override
+		{
+			auto const offset = ((y * width) + x) * 3;
+			return nes::rgb{ back_buffer_[offset + 0], back_buffer_[offset + 1], back_buffer_[offset + 2] };
+		}
+
+		auto set(unsigned const x, unsigned const y, nes::rgb const value) -> void override
+		{
+			auto const offset = ((y * width) + x) * 3;
+			back_buffer_[offset + 0] = value.r;
+			back_buffer_[offset + 1] = value.g;
+			back_buffer_[offset + 2] = value.b;
+		}
+
+		auto switch_buffers() -> void override
+		{
+			std::swap(front_buffer_, back_buffer_);
+		}
+	};
+} // namespace
+
+int main()
+{
+	auto const path = "/Users/hannes/Documents/temp/supermario.nes";
+
+	auto cartridge = nes::cartridge::from_file(path);
+	if (!cartridge.is_valid())
+	{
+		std::cerr << "Could not load cartridge!" << std::endl;
+		std::abort();
+	}
+
+	// Initialize the system to be tested.
+	auto display_a = std::make_unique<dummy_display>();
+	auto sys_a = nes::nes{ cartridge, *display_a };
+
+	// Initialize the (assumed to be working) reference implementation.
+	auto display_b = std::make_unique<dummy_display>();
+	auto sys_b = nes::nes{ cartridge, *display_b };
+
+	// Run.
+	while (true)
+	{
+		auto const status_a = sys_a.get_snapshot();
+		auto const status_b = sys_b.get_snapshot();
+
+		if (status_a != status_b)
+		{
+			std::cout << "Different snapshot!\n";
+			return 1;
+		}
+
+		std::cout << "Cycle: " << status_a.cpu_cycle.to_cpu() << ", " << status_b.cpu_cycle.to_cpu() << '\n';
+
+		sys_a.step_to_nmi();
+		sys_b.step_to_nmi();
+	}
+}
\ No newline at end of file
diff --git a/lib/CMakeLists.txt b/lib/CMakeLists.txt
new file mode 100644
index 0000000..e98002c
--- /dev/null
+++ b/lib/CMakeLists.txt
@@ -0,0 +1,21 @@
+add_library(nes STATIC)
+add_library(nes::nes ALIAS nes)
+
+target_include_directories(nes PUBLIC .)
+target_link_libraries(nes PRIVATE nes::options)
+
+if(NES_ENABLE_PPU)
+	target_compile_definitions(nes PUBLIC NES_ENABLE_PPU)
+endif()
+if(NES_ENABLE_DEBUG_OUTPUT)
+	target_compile_definitions(nes PUBLIC NES_ENABLE_DEBUG_OUTPUT)
+	target_link_libraries(nes PUBLIC spdlog::spdlog)
+endif()
+
+add_library(nes_ref STATIC)
+add_library(nes::ref ALIAS nes_ref)
+
+target_link_libraries(nes_ref PRIVATE nes::options)
+target_link_libraries(nes_ref PUBLIC nes::nes)
+
+add_subdirectory(nes)
\ No newline at end of file
diff --git a/lib/nes/CMakeLists.txt b/lib/nes/CMakeLists.txt
new file mode 100644
index 0000000..78b7d04
--- /dev/null
+++ b/lib/nes/CMakeLists.txt
@@ -0,0 +1,20 @@
+target_sources(
+	nes
+	PRIVATE
+		nes.hh
+		nes.cc
+		cartridge.hh
+		cartridge.cc
+		display.hh
+		display.cc
+		controller.hh
+		controller.cc
+		cpu.hh
+		cpu.cc
+		ppu.hh
+		ppu.cc
+		mapper.hh
+		mapper.cc)
+
+add_subdirectory(util)
+add_subdirectory(ref)
\ No newline at end of file
diff --git a/src/nes/cartridge.cc b/lib/nes/cartridge.cc
index 861dc13..861dc13 100644
--- a/src/nes/cartridge.cc
+++ b/lib/nes/cartridge.cc
diff --git a/src/nes/cartridge.hh b/lib/nes/cartridge.hh
index 3ce2a16..3ce2a16 100644
--- a/src/nes/cartridge.hh
+++ b/lib/nes/cartridge.hh
diff --git a/src/nes/controller.cc b/lib/nes/controller.cc
index 87842e2..d9d6946 100644
--- a/src/nes/controller.cc
+++ b/lib/nes/controller.cc
@@ -7,7 +7,7 @@ namespace nes
 		auto const res = index_ < 8 ? (pressed_.get_raw_value() >> index_) & 1 : 0;
 		index_ += 1;
 		if (strobing_) { index_ = 0; }
-		return res;
+		return static_cast<std::uint8_t>(res);
 	}
 
 	auto controller::write(std::uint8_t const value) -> void
diff --git a/src/nes/controller.hh b/lib/nes/controller.hh
index fa16859..fa16859 100644
--- a/src/nes/controller.hh
+++ b/lib/nes/controller.hh
diff --git a/src/nes/cpu.cc b/lib/nes/cpu.cc
index 9060e72..51507b0 100644
--- a/src/nes/cpu.cc
+++ b/lib/nes/cpu.cc
@@ -2,8 +2,7 @@
 #include "nes/ppu.hh"
 #include "nes/controller.hh"
 #include "nes/mapper.hh"
-
-#define ENABLE_PPU
+#include "nes/util/snapshot.hh"
 
 namespace nes
 {
@@ -16,7 +15,7 @@ namespace nes
 		registers_.pc = read16(address{ 0xFFFC });
 	}
 
-	auto cpu::snapshot(test::status& snapshot) -> void
+	auto cpu::build_snapshot(snapshot& snapshot) -> void
 	{
 		snapshot.cpu_cycle = current_cycles_;
 		snapshot.ram = std::vector(std::begin(ram_), std::end(ram_));
@@ -49,13 +48,13 @@ namespace nes
 	{
 		// See https://www.nesdev.org/wiki/CPU_unofficial_opcodes
 
+#ifdef NES_ENABLE_PPU
 		if (nmi_pending_)
 		{
-#ifdef ENABLE_PPU
 			execute_interrupt(address{ 0xFFFA });
-#endif
 			nmi_pending_ = false;
 		}
+#endif
 
 		auto const opcode = advance_pc8();
 		switch (opcode)
@@ -1261,7 +1260,7 @@ namespace nes
 	auto cpu::fetch_operand<cpu::addressing_mode::immediate>(force_page_crossing)
 		-> operand<addressing_mode::immediate>
 	{
-		return operand<addressing_mode::immediate>{ *this, advance_pc8() };
+		return operand<addressing_mode::immediate>{ advance_pc8() };
 	}
 
 	// -----------------------------------------------------------------------------------------------------------------
@@ -1277,7 +1276,7 @@ namespace nes
 		if (addr <= address{ 0x1FFF }) { return ram_[addr.get_absolute() % ram_size]; }
 		if (addr <= address{ 0x3FFF })
 		{
-#ifdef ENABLE_PPU
+#ifdef NES_ENABLE_PPU
 			switch (addr.get_absolute() % 8)
 			{
 				case 0: return ppu_.read_latch();
@@ -1295,7 +1294,7 @@ namespace nes
 #endif
 		}
 		if (addr <= address{ 0x4013 }) { return 0x0; } // TODO: APU registers
-#ifdef ENABLE_PPU
+#ifdef NES_ENABLE_PPU
 		if (addr == address{ 0x4014 }) { return ppu_.read_latch(); }
 #else
 		if (addr == address{ 0x4014 }) { return 0x0; }
@@ -1319,7 +1318,7 @@ namespace nes
 		if (addr <= address{ 0x1FFF }) { ram_[addr.get_absolute() % ram_size] = value; return; }
 		if (addr <= address{ 0x3FFF })
 		{
-#ifdef ENABLE_PPU
+#ifdef NES_ENABLE_PPU
 			switch (addr.get_absolute() % 8)
 			{
 				case 0: ppu_.write_ppuctrl(value); return;
@@ -1337,7 +1336,7 @@ namespace nes
 #endif
 		}
 		if (addr <= address{ 0x4013 }) { return; } // TODO: APU registers
-#ifdef ENABLE_PPU
+#ifdef NES_ENABLE_PPU
 		if (addr == address{ 0x4014 }) { ppu_.write_oamdma(value); return; }
 #else
 		if (addr == address{ 0x4014 }) { return; }
diff --git a/src/nes/cpu.hh b/lib/nes/cpu.hh
index fc3ef5b..9511c09 100644
--- a/src/nes/cpu.hh
+++ b/lib/nes/cpu.hh
@@ -1,14 +1,14 @@
 #pragma once
 
-#include "nes/util/cycle_count.hh"
+#include "nes/util/cycle-count.hh"
 #include "nes/util/address.hh"
-#include "status.hh"
 
 namespace nes
 {
 	class ppu;
 	class controller;
 	class mapper;
+	struct snapshot;
 
 	class cpu
 	{
@@ -110,13 +110,11 @@ namespace nes
 		template<>
 		class operand<addressing_mode::immediate>
 		{
-			cpu& cpu_;
 			std::uint8_t value_{ 0 };
 
 		public:
-			explicit operand(cpu& cpu, std::uint8_t const value)
-				: cpu_{ cpu }
-			, value_{ value }
+			explicit operand(std::uint8_t const value)
+				: value_{ value }
 			{
 			}
 
@@ -132,9 +130,8 @@ namespace nes
 		auto operator=(cpu const&) -> cpu& = delete;
 		auto operator=(cpu&&) -> cpu& = delete;
 
-		auto snapshot(test::status&) -> void;
-
 		auto get_cycles() const -> cycle_count { return current_cycles_; }
+		auto build_snapshot(snapshot&) -> void;
 		auto stall_cycles(cycle_count) -> void;
 		auto trigger_nmi() -> void;
 		auto step() -> void;
diff --git a/src/nes/display.cc b/lib/nes/display.cc
index 4ff1d5f..4ff1d5f 100644
--- a/src/nes/display.cc
+++ b/lib/nes/display.cc
diff --git a/src/nes/display.hh b/lib/nes/display.hh
index 14ccff1..14ccff1 100644
--- a/src/nes/display.hh
+++ b/lib/nes/display.hh
diff --git a/src/nes/mapper.cc b/lib/nes/mapper.cc
index 5392d87..9346be7 100644
--- a/src/nes/mapper.cc
+++ b/lib/nes/mapper.cc
@@ -16,11 +16,6 @@ namespace nes
 	{
 	}
 
-	auto mapper::snapshot(test::status& snapshot) const -> void
-	{
-		snapshot.chrrom = std::vector(cartridge_.get_chr_rom(), cartridge_.get_chr_rom() + cartridge_.get_chr_rom_length());
-	}
-
 	auto mapper::select(cartridge& cartridge) -> mapper
 	{
 		switch (cartridge.get_mapper_number())
diff --git a/src/nes/mapper.hh b/lib/nes/mapper.hh
index 12ad804..f2873a6 100644
--- a/src/nes/mapper.hh
+++ b/lib/nes/mapper.hh
@@ -1,7 +1,6 @@
 #pragma once
 
 #include "nes/util/address.hh"
-#include "status.hh"
 
 namespace nes
 {
@@ -28,8 +27,6 @@ namespace nes
 		auto operator=(mapper const&) -> mapper& = delete;
 		auto operator=(mapper&&) -> mapper& = delete;
 
-		auto snapshot(test::status&) const -> void;
-
 		auto read_cpu(address const addr) -> std::uint8_t
 		{
 			return (this->*read_cpu_)(addr);
diff --git a/src/nes/nes.cc b/lib/nes/nes.cc
index 7ac1887..01e339d 100644
--- a/src/nes/nes.cc
+++ b/lib/nes/nes.cc
@@ -2,6 +2,7 @@
 #include "nes/mapper.hh"
 #include "nes/display.hh"
 #include "nes/util/rgb.hh"
+#include "nes/util/snapshot.hh"
 #include <iostream>
 
 namespace nes
@@ -62,13 +63,12 @@ namespace nes
 		}
 	}
 
-	auto nes::snapshot() -> test::status
+	auto nes::get_snapshot() -> snapshot
 	{
-		auto res = test::status{};
+		auto res = snapshot{};
 		res.sram = std::vector(cartridge_.get_ram(), cartridge_.get_ram() + cartridge_.get_ram_length());
-		cpu_.snapshot(res);
-		ppu_.snapshot(res);
-		mapper_.snapshot(res);
+		cpu_.build_snapshot(res);
+		ppu_.build_snapshot(res);
 		return res;
 	}
 } // namespace nes
\ No newline at end of file
diff --git a/src/nes/nes.hh b/lib/nes/nes.hh
index 76c29ab..fe57cd4 100644
--- a/src/nes/nes.hh
+++ b/lib/nes/nes.hh
@@ -1,16 +1,16 @@
 #pragma once
 
-#include "nes/util/cycle_count.hh"
+#include "nes/util/cycle-count.hh"
 #include "nes/cartridge.hh"
 #include "nes/controller.hh"
 #include "nes/cpu.hh"
 #include "nes/ppu.hh"
 #include "nes/mapper.hh"
-#include "status.hh"
 
 namespace nes
 {
 	class display;
+	struct snapshot;
 
 	/// The main console abstraction.
 	class nes
@@ -36,12 +36,11 @@ namespace nes
 		auto get_controller_1() -> controller& { return controller_1_; }
 		auto get_controller_2() const -> controller const& { return controller_2_; }
 		auto get_controller_2() -> controller& { return controller_2_; }
-		auto ref_operations() -> std::vector<test::memory_operation>& { return ppu_.memory_operations; }
 
 		auto step(std::chrono::microseconds delta) -> void;
 		auto step(cycle_count delta) -> void;
 		auto step_to_nmi() -> void; // XXX: Debugging
 
-		auto snapshot() -> test::status;
+		auto get_snapshot() -> snapshot;
 	};
 } // namespace nes
\ No newline at end of file
diff --git a/src/nes/ppu.cc b/lib/nes/ppu.cc
index 87c7f8d..3170de9 100644
--- a/src/nes/ppu.cc
+++ b/lib/nes/ppu.cc
@@ -4,9 +4,8 @@
 #include "nes/mapper.hh"
 #include "nes/util/address.hh"
 #include "nes/util/rgb.hh"
-#include <iostream>
-
-// #define ENABLE_TRACES
+#include "nes/util/snapshot.hh"
+#include "nes/util/debug.hh"
 
 namespace nes
 {
@@ -17,7 +16,7 @@ namespace nes
 	{
 	}
 
-	auto ppu::snapshot(test::status& snapshot) -> void
+	auto ppu::build_snapshot(snapshot& snapshot) -> void
 	{
 		snapshot.vram = std::vector(std::begin(vram_), std::end(vram_));
 		snapshot.oam = std::vector(std::begin(oam_), std::end(oam_));
@@ -137,7 +136,6 @@ namespace nes
 		if (pre_line && scanline_cycle_ == 1)
 		{
 			status_.vblank = false;
-			nmi_change();
 			status_.sprite_zero_hit = false;
 			status_.sprite_overflow = false;
 		}
@@ -461,13 +459,10 @@ namespace nes
 	{
 		auto const base = latch_ & ~status_mask;
 		auto const res = base | (status_.value & status_mask);
-#ifdef ENABLE_TRACES
-		memory_operations.emplace_back(test::memory_operation::type::read_ppustatus, res, current_cycles_);
-#endif
+		NES_DEBUG_LOG(ppu, "PPUSTATUS -> {:#2x}", res);
 
 		status_.vblank = false;
 		internal_.w = false;
-		nmi_change();
 
 		write_latch(res);
 		return res;
@@ -480,9 +475,7 @@ namespace nes
 		{
 			res &= 0xE3;
 		}
-#ifdef ENABLE_TRACES
-		memory_operations.emplace_back(test::memory_operation::type::read_oamdata, res, current_cycles_);
-#endif
+		NES_DEBUG_LOG(ppu, "OAMDATA -> {:#2x}", res);
 		write_latch(res);
 		return res;
 	}
@@ -503,9 +496,7 @@ namespace nes
 			ppudata_read_buffer_ = read8(addr - 0x1000);
 		}
 
-#ifdef ENABLE_TRACES
-		memory_operations.emplace_back(test::memory_operation::type::read_ppudata, res, current_cycles_);
-#endif
+		NES_DEBUG_LOG(ppu, "PPUDATA -> {:#2x}", res);
 		increment_vram();
 		return res;
 	}
@@ -517,26 +508,22 @@ namespace nes
 
 	auto ppu::write_ppuctrl(std::uint8_t const value) -> void
 	{
+		write_latch(value);
 		if (current_cycles_ > boot_up_cycles)
 		{
-			write_latch(value);
+			NES_DEBUG_LOG(ppu, "PPUCTRL <- {:#2x}", value);
 			control_.value = value;
 			internal_.t = (internal_.t & 0xF3FF) | ((value & 0x03) << 10);
-#ifdef ENABLE_TRACES
-			memory_operations.emplace_back(test::memory_operation::type::write_ppuctrl, value, current_cycles_);
-#endif
 			nmi_change();
 		}
 	}
 
 	auto ppu::write_ppuscroll(std::uint8_t const value) -> void
 	{
+		write_latch(value);
 		if (current_cycles_ > boot_up_cycles)
 		{
-			write_latch(value);
-#ifdef ENABLE_TRACES
-			memory_operations.emplace_back(test::memory_operation::type::write_ppuscroll, value, current_cycles_);
-#endif
+			NES_DEBUG_LOG(ppu, "PPUSCROLL <- {:#2x}", value);
 			if (!internal_.w)
 			{
 				// First write -> x value.
@@ -556,24 +543,20 @@ namespace nes
 
 	auto ppu::write_ppumask(std::uint8_t const value) -> void
 	{
+		write_latch(value);
 		if (current_cycles_ > boot_up_cycles)
 		{
-			write_latch(value);
-#ifdef ENABLE_TRACES
-			memory_operations.emplace_back(test::memory_operation::type::write_ppumask, value, current_cycles_);
-#endif
+			NES_DEBUG_LOG(ppu, "PPUMASK <- {:#2x}", value);
 			mask_.value = value;
 		}
 	}
 
 	auto ppu::write_ppuaddr(std::uint8_t const value) -> void
 	{
+		write_latch(value);
 		if (current_cycles_ > boot_up_cycles)
 		{
-			write_latch(value);
-#ifdef ENABLE_TRACES
-			memory_operations.emplace_back(test::memory_operation::type::write_ppuaddr, value, current_cycles_);
-#endif
+			NES_DEBUG_LOG(ppu, "PPUADDR <- {:#2x}", value);
 			if (!internal_.w)
 			{
 				// First write.
@@ -592,9 +575,7 @@ namespace nes
 
 	auto ppu::write_ppudata(std::uint8_t const value) -> void
 	{
-#ifdef ENABLE_TRACES
-		memory_operations.emplace_back(test::memory_operation::type::write_ppudata, value, current_cycles_);
-#endif
+		NES_DEBUG_LOG(ppu, "PPUDATA <- {:#2x} (address: {:#4x})", value, internal_.v);
 		write_latch(value);
 		write8(address{ internal_.v }, value);
 		increment_vram();
@@ -602,18 +583,14 @@ namespace nes
 
 	auto ppu::write_oamaddr(std::uint8_t const value) -> void
 	{
-#ifdef ENABLE_TRACES
-		memory_operations.emplace_back(test::memory_operation::type::write_oamaddr, value, current_cycles_);
-#endif
+		NES_DEBUG_LOG(ppu, "OAMADDR <- {:#2x}", value);
 		write_latch(value);
 		oamaddr_ = value;
 	}
 
 	auto ppu::write_oamdata(std::uint8_t const value) -> void
 	{
-#ifdef ENABLE_TRACES
-		memory_operations.emplace_back(test::memory_operation::type::write_oamdata, value, current_cycles_);
-#endif
+		NES_DEBUG_LOG(ppu, "OAMDATA <- {:#2x}", value);
 		write_latch(value);
 		oam_[oamaddr_] = value;
 		oamaddr_ += 1;
@@ -622,9 +599,7 @@ namespace nes
 	auto ppu::write_oamdma(std::uint8_t const value) -> void
 	{
 		// TODO: Do this in CPU::step instead in case there's an NMI?
-#ifdef ENABLE_TRACES
-		memory_operations.emplace_back(test::memory_operation::type::write_oamdma, value, current_cycles_);
-#endif
+		NES_DEBUG_LOG(ppu, "OAMDMA <- {:#2x}", value);
 		auto addr = address{ value, 0x00 };
 		for (auto i = unsigned{ 0 }; i < 256; ++i)
 		{
@@ -643,8 +618,7 @@ namespace nes
 
 	auto ppu::nmi_change() -> void
 	{
-		auto const should_trigger = control_.vblank_nmi && status_.vblank;
-		if (should_trigger)
+		if (control_.vblank_nmi && status_.vblank)
 		{
 			cpu_.trigger_nmi();
 		}
diff --git a/src/nes/ppu.hh b/lib/nes/ppu.hh
index fff51de..d7d9baa 100644
--- a/src/nes/ppu.hh
+++ b/lib/nes/ppu.hh
@@ -1,7 +1,6 @@
 #pragma once
 
-#include "nes/util/cycle_count.hh"
-#include "status.hh"
+#include "nes/util/cycle-count.hh"
 
 namespace nes
 {
@@ -10,6 +9,7 @@ namespace nes
 	class mapper;
 	class display;
 	class rgb;
+	struct snapshot;
 
 	class ppu
 	{
@@ -148,7 +148,6 @@ namespace nes
 		std::uint8_t high_tile_byte_{ 0 };
 		sprite sprites_[8]{}; // Evaluated sprites.
 		unsigned sprite_count_{ 0 }; // Number of evaluated sprites in sprites_.
-		bool nmi_requested_{ false };
 
 	public:
 		explicit ppu(cpu&, mapper&, display&);
@@ -158,10 +157,8 @@ namespace nes
 		auto operator=(ppu const&) -> ppu& = delete;
 		auto operator=(ppu&&) -> ppu& = delete;
 
-		std::vector<test::memory_operation> memory_operations;
-
 		auto get_cycles() const -> cycle_count { return current_cycles_; }
-		auto snapshot(test::status&) -> void;
+		auto build_snapshot(snapshot&) -> void;
 		auto step() -> void;
 
 		// Memory access
diff --git a/lib/nes/ref/CMakeLists.txt b/lib/nes/ref/CMakeLists.txt
new file mode 100644
index 0000000..ab8e74d
--- /dev/null
+++ b/lib/nes/ref/CMakeLists.txt
@@ -0,0 +1,4 @@
+target_sources(
+	nes_ref
+	PRIVATE
+		test.cc)
\ No newline at end of file
diff --git a/lib/nes/ref/test.cc b/lib/nes/ref/test.cc
new file mode 100644
index 0000000..210ece0
--- /dev/null
+++ b/lib/nes/ref/test.cc
@@ -0,0 +1,3 @@
+//
+// Created by Hannes Schulze on 23.01.25.
+//
diff --git a/src/nes/util/CMakeLists.txt b/lib/nes/util/CMakeLists.txt
index adaa80c..0fdb0ba 100644
--- a/src/nes/util/CMakeLists.txt
+++ b/lib/nes/util/CMakeLists.txt
@@ -3,5 +3,7 @@ target_sources(
     PRIVATE
         address.hh
         button-mask.hh
-        cycle_count.hh
-        rgb.hh)
\ No newline at end of file
+        cycle-count.hh
+		debug.hh
+        rgb.hh
+		snapshot.hh)
\ No newline at end of file
diff --git a/src/nes/util/address.hh b/lib/nes/util/address.hh
index 7987d07..7987d07 100644
--- a/src/nes/util/address.hh
+++ b/lib/nes/util/address.hh
diff --git a/src/nes/util/button-mask.hh b/lib/nes/util/button-mask.hh
index b010b9e..b010b9e 100644
--- a/src/nes/util/button-mask.hh
+++ b/lib/nes/util/button-mask.hh
diff --git a/src/nes/util/cycle_count.hh b/lib/nes/util/cycle-count.hh
index 8afd40a..f1a4a7e 100644
--- a/src/nes/util/cycle_count.hh
+++ b/lib/nes/util/cycle-count.hh
@@ -35,7 +35,7 @@ namespace nes
 
 		static constexpr auto from_duration(std::chrono::microseconds const duration) -> cycle_count
 		{
-			return from_units(duration.count() * second().get_units() / (1000 * 1000));
+			return from_units(static_cast<std::uint64_t>(duration.count()) * second().get_units() / (1000 * 1000));
 		}
 
 		static constexpr auto from_cpu(std::uint64_t const cpu_cycles) -> cycle_count
diff --git a/lib/nes/util/debug.hh b/lib/nes/util/debug.hh
new file mode 100644
index 0000000..409d55a
--- /dev/null
+++ b/lib/nes/util/debug.hh
@@ -0,0 +1,15 @@
+#pragma once
+
+#ifdef NES_ENABLE_DEBUG_OUTPUT
+
+#include <spdlog/spdlog.h>
+
+#define NES_DEBUG_LOG(name, ...) \
+  spdlog::info("[" #name "] " __VA_ARGS__)
+
+#else
+
+#define NES_DEBUG_LOG(name, fmt, ...) \
+  (void)0
+
+#endif
\ No newline at end of file
diff --git a/src/nes/util/rgb.hh b/lib/nes/util/rgb.hh
index d62c70c..d62c70c 100644
--- a/src/nes/util/rgb.hh
+++ b/lib/nes/util/rgb.hh
diff --git a/lib/nes/util/snapshot.hh b/lib/nes/util/snapshot.hh
new file mode 100644
index 0000000..de23a46
--- /dev/null
+++ b/lib/nes/util/snapshot.hh
@@ -0,0 +1,63 @@
+#pragma once
+
+#include "nes/util/cycle-count.hh"
+#include <vector>
+#include <cstdint>
+
+namespace nes
+{
+	/// System snapshot used for comparison with a reference implementation.
+	struct snapshot
+	{
+		explicit snapshot() = default;
+
+		cycle_count cpu_cycle;
+		cycle_count ppu_cycle;
+		std::vector<std::uint8_t> ram;
+		std::vector<std::uint8_t> sram;
+		std::vector<std::uint8_t> vram;
+		std::vector<std::uint8_t> oam;
+		struct
+		{
+			std::uint16_t pc{};
+			std::uint8_t sp{};
+			std::uint8_t a{};
+			std::uint8_t x{};
+			std::uint8_t y{};
+			std::uint8_t p{};
+			bool c{};
+			bool z{};
+			bool i{};
+			bool d{};
+			bool b{};
+			bool v{};
+			bool n{};
+		} registers{};
+	};
+
+	inline auto operator==(snapshot const& a, snapshot const& b) -> bool
+	{
+		if (a.cpu_cycle != b.cpu_cycle) { return false; }
+		if (a.ppu_cycle != b.ppu_cycle) { return false; }
+		if (a.ram != b.ram) { return false; }
+		if (a.sram != b.sram) { return false; }
+		if (a.vram != b.vram) { return false; }
+		if (a.oam != b.oam) { return false; }
+		if (a.registers.pc != b.registers.pc) { return false; }
+		if (a.registers.sp != b.registers.sp) { return false; }
+		if (a.registers.a != b.registers.a) { return false; }
+		if (a.registers.x != b.registers.x) { return false; }
+		if (a.registers.y != b.registers.y) { return false; }
+		if (a.registers.p != b.registers.p) { return false; }
+		if (a.registers.c != b.registers.c) { return false; }
+		if (a.registers.z != b.registers.z) { return false; }
+		if (a.registers.i != b.registers.i) { return false; }
+		if (a.registers.d != b.registers.d) { return false; }
+		if (a.registers.b != b.registers.b) { return false; }
+		if (a.registers.v != b.registers.v) { return false; }
+		if (a.registers.n != b.registers.n) { return false; }
+		return true;
+	}
+
+	inline auto operator!=(snapshot const& a, snapshot const& b) -> bool { return !(a == b); }
+} // namespace nes
\ No newline at end of file
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
deleted file mode 100644
index b997a1d..0000000
--- a/src/CMakeLists.txt
+++ /dev/null
@@ -1,13 +0,0 @@
-add_subdirectory(nes)
-#add_subdirectory(ref)
-#add_subdirectory(test)
-
-target_sources(
-    nes
-    PRIVATE
-        main.mm
-        status.hh
-        scene.hh
-        scene.mm)
-
-target_include_directories(nes PRIVATE .)
\ No newline at end of file
diff --git a/src/nes/CMakeLists.txt b/src/nes/CMakeLists.txt
deleted file mode 100644
index fcdcb07..0000000
--- a/src/nes/CMakeLists.txt
+++ /dev/null
@@ -1,19 +0,0 @@
-add_subdirectory(util)
-
-target_sources(
-    nes
-    PRIVATE
-        nes.hh
-        nes.cc
-        cartridge.hh
-        cartridge.cc
-        display.hh
-        display.cc
-        controller.hh
-        controller.cc
-        cpu.hh
-        cpu.cc
-        ppu.hh
-        ppu.cc
-        mapper.hh
-        mapper.cc)
\ No newline at end of file
diff --git a/src/status.hh b/src/status.hh
deleted file mode 100644
index b56be58..0000000
--- a/src/status.hh
+++ /dev/null
@@ -1,97 +0,0 @@
-#pragma once
-
-#include "nes/util/cycle_count.hh"
-#include <vector>
-#include <cstdint>
-
-namespace test
-{
-	/// System status used for comparison.
-	struct status
-	{
-		explicit status() = default;
-
-		nes::cycle_count cpu_cycle;
-		std::vector<std::uint8_t> ram;
-		std::vector<std::uint8_t> sram;
-		std::vector<std::uint8_t> vram;
-		std::vector<std::uint8_t> oam;
-		std::vector<std::uint8_t> chrrom;
-		struct
-		{
-			std::uint16_t pc{};
-			std::uint8_t sp{};
-			std::uint8_t a{};
-			std::uint8_t x{};
-			std::uint8_t y{};
-			std::uint8_t p{};
-			bool c{};
-			bool z{};
-			bool i{};
-			bool d{};
-			bool b{};
-			bool v{};
-			bool n{};
-		} registers{};
-
-		static auto equal(status const& a, status const& b) -> bool
-		{
-			if (a.cpu_cycle != b.cpu_cycle) { return false; }
-			if (a.ram != b.ram) { return false; }
-			if (a.sram != b.sram) { return false; }
-			if (a.registers.pc != b.registers.pc) { return false; }
-			if (a.registers.sp != b.registers.sp) { return false; }
-			if (a.registers.a != b.registers.a) { return false; }
-			if (a.registers.x != b.registers.x) { return false; }
-			if (a.registers.y != b.registers.y) { return false; }
-			if (a.registers.p != b.registers.p) { return false; }
-			if (a.registers.c != b.registers.c) { return false; }
-			if (a.registers.z != b.registers.z) { return false; }
-			if (a.registers.i != b.registers.i) { return false; }
-			if (a.registers.d != b.registers.d) { return false; }
-			if (a.registers.b != b.registers.b) { return false; }
-			if (a.registers.v != b.registers.v) { return false; }
-			if (a.registers.n != b.registers.n) { return false; }
-			return true;
-		}
-	};
-
-	struct memory_operation
-	{
-		enum class type
-		{
-			read_ppustatus,
-			read_oamdata,
-			read_ppudata,
-			write_ppuctrl,
-			write_ppuscroll,
-			write_ppumask,
-			write_ppuaddr,
-			write_ppudata,
-			write_oamaddr,
-			write_oamdata,
-			write_oamdma,
-		};
-
-		explicit constexpr memory_operation(type const t, std::uint8_t const v, nes::cycle_count cycles)
-			: t{ t }
-			, v{ v }
-			, cycles{ cycles }
-		{
-		}
-
-		type t{};
-		std::uint8_t v{};
-		nes::cycle_count cycles;
-	};
-
-	constexpr auto operator==(memory_operation const a, memory_operation const b) -> bool
-	{
-		return a.t == b.t && a.v == b.v;
-	}
-
-	constexpr auto operator!=(memory_operation const a, memory_operation const b) -> bool
-	{
-		return a.t != b.t || a.v != b.v;
-	}
-} // namespace test
\ No newline at end of file
diff --git a/src/test/CMakeLists.txt b/src/test/CMakeLists.txt
deleted file mode 100644
index e69de29..0000000
--- a/src/test/CMakeLists.txt
+++ /dev/null
diff --git a/src/test/main.cc b/src/test/main.cc
deleted file mode 100644
index 58e618d..0000000
--- a/src/test/main.cc
+++ /dev/null
@@ -1,3 +0,0 @@
-//
-// Created by Hannes Schulze on 17.01.25.
-//