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diff --git a/reduced_system_layer.c b/reduced_system_layer.c
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+#if 0 /*
+#/  ================================================================
+#/
+#/    reduced_system_layer.c
+#/
+#/  This is a reduced system layer.
+#/  It allows you to create a window, draw graphics in it, handle
+#/  input events.
+#/
+#/  ----------------------------------------------------------------
+#/
+#/  DESIGN PRINCIPLES
+#/
+#/  - Minimalistic feature set. For graphics, you have access to the
+#/    pixel buffer, and that's it.
+#/
+#/  - No implicit control flow. No callbacks. You write your own
+#/    main and call everything explicitly. But the number of things
+#/    you have to call to do something is as little as possible.
+#/
+#/  - Optimized to use in a single source file.
+#/    Installation process? Ctrl+C, Ctrl+V, done.
+#/
+#/  If you have an idea how to reduce the feature set further,
+#/  let me know!
+#/
+#/  ----------------------------------------------------------------
+#/
+#/    (C) 2024 Mitya Selivanov <guattari.tech>, MIT License
+#/
+#/  ================================================================
+#/
+#/    Self-compilation shell script
+#/
+SRC=${0##*./}
+BIN=${SRC%.*}
+gcc                                         \
+  -Wall -Wextra -Werror -pedantic           \
+  -Wno-old-style-declaration                \
+  -Wno-missing-braces                       \
+  -Wno-unused-variable                      \
+  -Wno-unused-but-set-variable              \
+  -Wno-unused-parameter                     \
+  -O3                                       \
+  -fsanitize=undefined,address,leak -mshstk \
+  -lX11 -lm                                 \
+  -o $BIN $SRC &&                           \
+  ./$BIN $@ && rm $BIN
+exit $? # */
+#endif
+//  ================================================================
+//
+//    Basic declarations
+//
+//  ================================================================
+
+#define _GNU_SOURCE
+
+typedef signed char        i8;
+typedef signed short       i16;
+typedef signed             i32;
+typedef signed long long   i64;
+typedef unsigned char      u8;
+typedef unsigned short     u16;
+typedef unsigned           u32;
+typedef unsigned long long u64;
+typedef char               c8;
+typedef signed char        b8;
+typedef float              f32;
+typedef double             f64;
+
+//  ================================================================
+//
+//    PLATFORM API
+//
+//  ================================================================
+
+enum {
+  MAX_NUM_PIXELS        = 4 * 1024 * 1024,
+  MAX_CLIPBOARD_SIZE    = 0,
+  MAX_NUM_AUDIO_SAMPLES = 0,
+  MAX_NUM_SOCKETS       = 0,
+
+  AUDIO_NUM_CHANNELS = 2,
+  AUDIO_SAMPLE_RATE  = 44100,
+
+  IPv4 = 1,
+  IPv6 = 2,
+  
+  BUTTON_LEFT = 256,
+  BUTTON_MIDDLE,
+  BUTTON_RIGHT,
+  KEY_LEFT,
+  KEY_RIGHT,
+  KEY_UP,
+  KEY_DOWN,
+  KEY_LCTRL,
+  KEY_RCTRL,
+  KEY_LSHIFT,
+  KEY_RSHIFT,
+  KEY_LALT,
+  KEY_RALT,
+  KEY_ESCAPE,
+  KEY_PRINTSCREEN,
+  KEY_DELETE,
+  KEY_PAUSE,
+  KEY_INSERT,
+  KEY_HOME,
+  KEY_END,
+  KEY_PAGEUP,
+  KEY_PAGEDOWN,
+  KEY_F_  = 256 * 2,
+  KEY_KP_ = 256 * 3,
+};
+
+typedef struct {
+  c8  *title;
+  i32  frame_width;
+  i32  frame_height;
+  u32 *pixels;
+  i64  clipboard_size;
+  c8  *clipboard; // TODO
+  b8   done;
+  b8   has_focus;
+  b8   has_cursor;
+  i32  cursor_x;
+  i32  cursor_y;
+  i32  cursor_dx;
+  i32  cursor_dy;
+  i64  wheel_dy;
+  b8   key_down[512];
+  b8   key_pressed[512];
+} Platform;
+
+typedef struct {
+  u16 type;
+  u16 port;
+  union {
+    u8 v4_address[4];
+    u8 v6_address[16];
+  };
+} IP_Address;
+
+typedef i64 (*Thread_Proc)(void *user_data);
+
+//  Window
+void p_init(void);
+void p_cleanup(void);
+i32  p_handle_events(void);
+
+//  Sound
+void p_handle_audio(i64 time_elapsed);
+void p_queue_sound(i64 delay, i64 num_samples, f32 *samples);
+
+//  UDP sockets
+i64 p_recv(u16 slot, IP_Address address, i64 size, u8 *data, IP_Address *remote_address);
+i64 p_send(u16 slot, IP_Address address, i64 size, u8 *data);
+
+Platform platform = {0};
+
+//  ================================================================
+//
+//    WRITE YOUR CODE HERE
+//
+//  ================================================================
+
+i32 main(i32 argc, c8 **argv) {
+  (void) argc;
+  (void) argv;
+
+  platform = (Platform) {
+    .title        = "Reduced System Layer",
+    .frame_width  = 960,
+    .frame_height = 720,
+  };
+
+  p_init();
+
+  while (!platform.done) {
+    p_handle_events();
+  }
+
+  p_cleanup();
+  return 0;
+}
+
+//  ================================================================
+//
+//    PLATFORM IMPLEMENTATION
+//
+//  ----------------------------------------------------------------
+//
+//  TODO
+//  - Clipboard
+//  - Sound
+//  - Sockets
+//
+//  X11 clipboard
+//  https://handmade.network/forums/articles/t/8544-implementing_copy_paste_in_x11
+//
+//  ALSA
+//  https://www.alsa-project.org/alsa-doc/alsa-lib/_2test_2pcm_min_8c-example.html
+//
+//  ================================================================
+//
+//  UDP sockets
+//
+//  ================================================================
+
+#include <assert.h>
+#include <string.h>
+
+i64 p_recv(u16 slot, IP_Address address, i64 size, u8 *data, IP_Address *remote_address) {
+  (void) slot;
+  (void) address;
+  (void) size;
+  (void) data;
+  (void) remote_address;
+  assert(0);
+  return 0;
+}
+
+i64 p_send(u16 slot, IP_Address address, i64 size, u8 *data) {
+  (void) slot;
+  (void) address;
+  (void) size;
+  (void) data;
+  assert(0);
+  return 0;
+}
+
+//  ================================================================
+//
+//  X11
+//
+//  ================================================================
+
+#ifdef __linux__
+
+#include <X11/Xlib.h>
+#include <X11/Xutil.h>
+
+static i16      _key_table[512];
+static u32      _buffer[MAX_NUM_PIXELS];
+static XImage   _image;
+static Display *_display;
+static GC       _gc;
+static Window   _window;
+static Atom     _wm_delete_window;
+
+void p_init(void) {
+  _display = XOpenDisplay(NULL);
+  assert(_display != NULL);
+
+  _key_table[XKeysymToKeycode(_display, XK_Left)]         = KEY_LEFT;
+  _key_table[XKeysymToKeycode(_display, XK_Right)]        = KEY_RIGHT;
+  _key_table[XKeysymToKeycode(_display, XK_Up)]           = KEY_UP;
+  _key_table[XKeysymToKeycode(_display, XK_Down)]         = KEY_DOWN;
+  _key_table[XKeysymToKeycode(_display, XK_1)]            = '1';
+  _key_table[XKeysymToKeycode(_display, XK_2)]            = '2';
+  _key_table[XKeysymToKeycode(_display, XK_3)]            = '3';
+  _key_table[XKeysymToKeycode(_display, XK_4)]            = '4';
+  _key_table[XKeysymToKeycode(_display, XK_5)]            = '5';
+  _key_table[XKeysymToKeycode(_display, XK_6)]            = '6';
+  _key_table[XKeysymToKeycode(_display, XK_7)]            = '7';
+  _key_table[XKeysymToKeycode(_display, XK_8)]            = '8';
+  _key_table[XKeysymToKeycode(_display, XK_9)]            = '9';
+  _key_table[XKeysymToKeycode(_display, XK_0)]            = '0';
+  _key_table[XKeysymToKeycode(_display, XK_A)]            = 'a';
+  _key_table[XKeysymToKeycode(_display, XK_B)]            = 'b';
+  _key_table[XKeysymToKeycode(_display, XK_C)]            = 'c';
+  _key_table[XKeysymToKeycode(_display, XK_D)]            = 'd';
+  _key_table[XKeysymToKeycode(_display, XK_E)]            = 'e';
+  _key_table[XKeysymToKeycode(_display, XK_F)]            = 'f';
+  _key_table[XKeysymToKeycode(_display, XK_G)]            = 'g';
+  _key_table[XKeysymToKeycode(_display, XK_H)]            = 'h';
+  _key_table[XKeysymToKeycode(_display, XK_I)]            = 'i';
+  _key_table[XKeysymToKeycode(_display, XK_J)]            = 'j';
+  _key_table[XKeysymToKeycode(_display, XK_K)]            = 'k';
+  _key_table[XKeysymToKeycode(_display, XK_L)]            = 'l';
+  _key_table[XKeysymToKeycode(_display, XK_M)]            = 'm';
+  _key_table[XKeysymToKeycode(_display, XK_N)]            = 'n';
+  _key_table[XKeysymToKeycode(_display, XK_O)]            = 'o';
+  _key_table[XKeysymToKeycode(_display, XK_P)]            = 'p';
+  _key_table[XKeysymToKeycode(_display, XK_Q)]            = 'q';
+  _key_table[XKeysymToKeycode(_display, XK_R)]            = 'r';
+  _key_table[XKeysymToKeycode(_display, XK_S)]            = 's';
+  _key_table[XKeysymToKeycode(_display, XK_T)]            = 't';
+  _key_table[XKeysymToKeycode(_display, XK_U)]            = 'u';
+  _key_table[XKeysymToKeycode(_display, XK_V)]            = 'v';
+  _key_table[XKeysymToKeycode(_display, XK_W)]            = 'w';
+  _key_table[XKeysymToKeycode(_display, XK_X)]            = 'x';
+  _key_table[XKeysymToKeycode(_display, XK_Y)]            = 'y';
+  _key_table[XKeysymToKeycode(_display, XK_Z)]            = 'z';
+  _key_table[XKeysymToKeycode(_display, XK_space)]        = ' ';
+  _key_table[XKeysymToKeycode(_display, XK_braceleft)]    = '[';
+  _key_table[XKeysymToKeycode(_display, XK_braceright)]   = ']';
+  _key_table[XKeysymToKeycode(_display, XK_colon)]        = ';';
+  _key_table[XKeysymToKeycode(_display, XK_quotedbl)]     = '\'';
+  _key_table[XKeysymToKeycode(_display, XK_asciitilde)]   = '`';
+  _key_table[XKeysymToKeycode(_display, XK_backslash)]    = '\\';
+  _key_table[XKeysymToKeycode(_display, XK_comma)]        = ',';
+  _key_table[XKeysymToKeycode(_display, XK_greater)]      = '.';
+  _key_table[XKeysymToKeycode(_display, XK_question)]     = '/';
+  _key_table[XKeysymToKeycode(_display, XK_F1)]           = KEY_F_ + 1;
+  _key_table[XKeysymToKeycode(_display, XK_F2)]           = KEY_F_ + 2;
+  _key_table[XKeysymToKeycode(_display, XK_F3)]           = KEY_F_ + 3;
+  _key_table[XKeysymToKeycode(_display, XK_F4)]           = KEY_F_ + 4;
+  _key_table[XKeysymToKeycode(_display, XK_F5)]           = KEY_F_ + 5;
+  _key_table[XKeysymToKeycode(_display, XK_F6)]           = KEY_F_ + 6;
+  _key_table[XKeysymToKeycode(_display, XK_F7)]           = KEY_F_ + 7;
+  _key_table[XKeysymToKeycode(_display, XK_F8)]           = KEY_F_ + 8;
+  _key_table[XKeysymToKeycode(_display, XK_F9)]           = KEY_F_ + 9;
+  _key_table[XKeysymToKeycode(_display, XK_F10)]          = KEY_F_ + 10;
+  _key_table[XKeysymToKeycode(_display, XK_F11)]          = KEY_F_ + 11;
+  _key_table[XKeysymToKeycode(_display, XK_F12)]          = KEY_F_ + 12;
+  _key_table[XKeysymToKeycode(_display, XK_Control_L)]    = KEY_LCTRL;
+  _key_table[XKeysymToKeycode(_display, XK_Control_R)]    = KEY_RCTRL;
+  _key_table[XKeysymToKeycode(_display, XK_Shift_L)]      = KEY_LSHIFT;
+  _key_table[XKeysymToKeycode(_display, XK_Shift_R)]      = KEY_RSHIFT;
+  _key_table[XKeysymToKeycode(_display, XK_Alt_L)]        = KEY_LALT;
+  _key_table[XKeysymToKeycode(_display, XK_Alt_R)]        = KEY_RALT;
+  _key_table[XKeysymToKeycode(_display, XK_Escape)]       = KEY_ESCAPE;
+  _key_table[XKeysymToKeycode(_display, XK_BackSpace)]    = '\b';
+  _key_table[XKeysymToKeycode(_display, XK_Tab)]          = '\t';
+  _key_table[XKeysymToKeycode(_display, XK_Return)]       = '\n';
+  _key_table[XKeysymToKeycode(_display, XK_Print)]        = KEY_PRINTSCREEN;
+  _key_table[XKeysymToKeycode(_display, XK_Delete)]       = KEY_DELETE;
+  _key_table[XKeysymToKeycode(_display, XK_Pause)]        = KEY_PAUSE;
+  _key_table[XKeysymToKeycode(_display, XK_Insert)]       = KEY_INSERT;
+  _key_table[XKeysymToKeycode(_display, XK_Home)]         = KEY_HOME;
+  _key_table[XKeysymToKeycode(_display, XK_End)]          = KEY_END;
+  _key_table[XKeysymToKeycode(_display, XK_Page_Up)]      = KEY_PAGEUP;
+  _key_table[XKeysymToKeycode(_display, XK_Page_Down)]    = KEY_PAGEDOWN;
+  _key_table[XKeysymToKeycode(_display, XK_KP_0)]         = KEY_KP_ + '0';
+  _key_table[XKeysymToKeycode(_display, XK_KP_1)]         = KEY_KP_ + '1';
+  _key_table[XKeysymToKeycode(_display, XK_KP_2)]         = KEY_KP_ + '2';
+  _key_table[XKeysymToKeycode(_display, XK_KP_3)]         = KEY_KP_ + '3';
+  _key_table[XKeysymToKeycode(_display, XK_KP_4)]         = KEY_KP_ + '4';
+  _key_table[XKeysymToKeycode(_display, XK_KP_5)]         = KEY_KP_ + '5';
+  _key_table[XKeysymToKeycode(_display, XK_KP_6)]         = KEY_KP_ + '6';
+  _key_table[XKeysymToKeycode(_display, XK_KP_7)]         = KEY_KP_ + '7';
+  _key_table[XKeysymToKeycode(_display, XK_KP_8)]         = KEY_KP_ + '8';
+  _key_table[XKeysymToKeycode(_display, XK_KP_9)]         = KEY_KP_ + '9';
+  _key_table[XKeysymToKeycode(_display, XK_KP_Enter)]     = KEY_KP_ + '\n';
+  _key_table[XKeysymToKeycode(_display, XK_KP_Divide)]    = KEY_KP_ + '/';
+  _key_table[XKeysymToKeycode(_display, XK_KP_Multiply)]  = KEY_KP_ + '*';
+  _key_table[XKeysymToKeycode(_display, XK_KP_Add)]       = KEY_KP_ + '+';
+  _key_table[XKeysymToKeycode(_display, XK_KP_Subtract)]  = KEY_KP_ + '-';
+  _key_table[XKeysymToKeycode(_display, XK_KP_Decimal)]   = KEY_KP_ + '.';
+  _key_table[XKeysymToKeycode(_display, XK_KP_Separator)] = KEY_KP_ + ',';
+
+  i32     screen = DefaultScreen(_display);
+  i32     depth  = DefaultDepth (_display, screen);
+  Visual *visual = DefaultVisual(_display, screen);
+
+  _gc = DefaultGC(_display, screen);
+
+  XSetGraphicsExposures(_display, _gc, False);
+
+  i32 _display_width  = DisplayWidth (_display, screen);
+  i32 _display_height = DisplayHeight(_display, screen);
+
+  i32 x = (_display_width  - platform.frame_width)  / 2;
+  i32 y = (_display_height - platform.frame_height) / 2;
+
+  _window = XCreateWindow(_display, XDefaultRootWindow(_display), x, y, platform.frame_width, platform.frame_height, 0, depth, InputOutput, visual, CWEventMask, &(XSetWindowAttributes) { .event_mask = KeyPressMask | KeyReleaseMask | ButtonPressMask | ButtonReleaseMask | EnterWindowMask | LeaveWindowMask | PointerMotionMask | VisibilityChangeMask | FocusChangeMask | StructureNotifyMask | SubstructureNotifyMask, });
+
+  platform.pixels = _buffer;
+
+  _image = (XImage) {
+    .width            = platform.frame_width,
+    .height           = platform.frame_height,
+    .depth            = depth,
+    .xoffset          = 0,
+    .format           = ZPixmap,
+    .data             = (c8 *) _buffer,
+    .byte_order       = LSBFirst,
+    .bitmap_unit      = 32,
+    .bitmap_bit_order = LSBFirst,
+    .bitmap_pad       = 32,
+    .bits_per_pixel   = 32,
+    .bytes_per_line   = 4 * platform.frame_width,
+    .red_mask         = 0xff0000,
+    .green_mask       = 0x00ff00,
+    .blue_mask        = 0x0000ff,
+  };
+
+
+  XInitImage(&_image);
+
+  _wm_delete_window = XInternAtom(_display, "WM_DELETE__WINDOW", False);
+
+  XSetWMProtocols(_display, _window, &_wm_delete_window, 1);
+
+  XStoreName(_display, _window, platform.title);
+  XMapWindow(_display, _window);
+}
+
+void p_cleanup(void) {
+  XDestroyWindow(_display, _window);
+  XCloseDisplay (_display);
+}
+
+i32 p_handle_events(void) {
+  XEvent            ev;
+  XWindowAttributes attrs;
+
+  XGetWindowAttributes(_display, _window, &attrs);
+
+  if (attrs.width == platform.frame_width && attrs.height == platform.frame_height)
+    XPutImage(_display, _window, _gc, &_image, 0, 0, 0, 0, attrs.width, attrs.height);
+
+  XFlush(_display);
+
+  i32 num_events = XEventsQueued(_display, QueuedAlready);
+
+  memset(platform.key_pressed, 0, sizeof platform.key_pressed);
+
+  platform.cursor_dx = 0;
+  platform.cursor_dy = 0;
+  platform.wheel_dy  = 0;
+
+  for (i32 i = 0; i < num_events; ++i) {
+    XNextEvent(_display, &ev);
+
+    switch (ev.type) {
+      case DestroyNotify:
+        platform.done = 1;
+        break;
+
+      case MotionNotify:
+        platform.cursor_dx += ev.xmotion.x - platform.cursor_x;
+        platform.cursor_dy += ev.xmotion.y - platform.cursor_y;
+        platform.cursor_x   = ev.xmotion.x;
+        platform.cursor_y   = ev.xmotion.y;
+        break;
+
+      case ButtonPress:
+        platform.cursor_x = ev.xbutton.x;
+        platform.cursor_y = ev.xbutton.y;
+        switch (ev.xbutton.button) {
+          case Button1:
+            platform.key_down[BUTTON_LEFT] = 1;
+            ++platform.key_pressed[BUTTON_LEFT];
+            break;
+          case Button2:
+            platform.key_down[BUTTON_MIDDLE] = 1;
+            ++platform.key_pressed[BUTTON_MIDDLE];
+            break;
+          case Button3:
+            platform.key_down[BUTTON_RIGHT] = 1;
+            ++platform.key_pressed[BUTTON_RIGHT];
+            break;
+          case Button4: ++platform.wheel_dy; break;
+          case Button5: --platform.wheel_dy; break;
+          default:;
+        }
+        break;
+
+      case ButtonRelease:
+        platform.cursor_x = ev.xbutton.x;
+        platform.cursor_y = ev.xbutton.y;
+        switch (ev.xbutton.button) {
+          case Button1: platform.key_down[BUTTON_LEFT]   = 0; break;
+          case Button2: platform.key_down[BUTTON_MIDDLE] = 0; break;
+          case Button3: platform.key_down[BUTTON_RIGHT]  = 0; break;
+          default:;
+        }
+        break;
+
+      case KeyPress:
+        platform.cursor_x = ev.xkey.x;
+        platform.cursor_y = ev.xkey.y;
+        platform.key_down   [_key_table[ev.xkey.keycode]] = 1;
+        platform.key_pressed[_key_table[ev.xkey.keycode]]++;
+        break;
+
+      case KeyRelease:
+        platform.cursor_x = ev.xkey.x;
+        platform.cursor_y = ev.xkey.y;
+        platform.key_down   [_key_table[ev.xkey.keycode]] = 0;
+        platform.key_pressed[_key_table[ev.xkey.keycode]]--;
+        break;
+
+      case EnterNotify: platform.has_cursor = 1; break;
+      case LeaveNotify: platform.has_cursor = 0; break;
+      case FocusIn:     platform.has_focus  = 1; break;
+      case FocusOut:    platform.has_focus  = 0; break;
+
+      case ClientMessage:
+        if ((Atom) ev.xclient.data.l[0] == _wm_delete_window)
+          platform.done = 1;
+        break;
+
+      default:;
+    }
+  }
+
+  if ((platform.frame_width != attrs.width || platform.frame_height != attrs.height) && attrs.width * attrs.height * 4 <= (i32) sizeof _buffer) {
+    if (attrs.width > 0 && attrs.height > 0) {
+      _image.width          = attrs.width;
+      _image.height         = attrs.height;
+      _image.bytes_per_line = 4 * attrs.width;
+    }
+
+    platform.frame_width  = attrs.width;
+    platform.frame_height = attrs.height;
+  }
+
+  return num_events;
+}
+
+#endif
+
+//  ================================================================
+//
+//  ALSA
+//
+//  ================================================================
+
+#ifdef __linux__
+
+void p_handle_audio(i64 time_elapsed) {
+  (void) time_elapsed;
+  assert(0);
+}
+
+void p_queue_sound(i64 delay, i64 num_samples, f32 *samples) {
+  (void) delay;
+  (void) num_samples;
+  (void) samples;
+  assert(0);
+}
+
+#endif