* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  background-color: #fff0f5;
}

/* Main layout: vertical stack, centred, full viewport height */
main {
  background-color: #fff0f5;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: flex-start;
  padding: 12px 20px 20px;
  gap: 16px;
  width: 100%;
}

/* Side-by-side layout: controls on the left, grid on the right */
/* max-width keeps the layout from stretching too wide on large screens */
.game-layout {
  display: flex;
  flex-direction: row;
  align-items: flex-start;
  gap: 24px;
  width: 100%;
  max-width: 1000px;
  justify-content: center;
}

/* Invisible spacer that mirrors the controls width on the right side */
/* This keeps the grid visually centred under the heading */
.game-layout::after {
  content: "";
  width: 160px;
  flex-shrink: 0;
}

/* clamp() scales the heading between 40px and 80px based on viewport width */
.game-heading {
  font-size: clamp(40px, 6vw, 80px);
  text-align: center;
  color: #aa336a;
}

/* Status message: whose turn, winner, draw, already taken */
/* clamp() scales between 20px and 50px */
#message {
  text-align: center;
  font-size: clamp(20px, 3vw, 50px);
  color: #00008b;
}

/* Sidebar: fixed width, full grid height, buttons pushed to top and bottom */
/* space-between pushes Start Again to align with the bottom of the grid */
.mode-controls {
  display: flex;
  flex-direction: column;
  gap: 16px;
  width: 160px;
  flex-shrink: 0;
  justify-content: space-between;
  height: min(500px, 55vh);
}

/* Wrapper that lets the grid column expand to fill remaining space */
.section-container {
  display: flex;
  justify-content: center;
  flex: 1;
}

/* Grid sizing uses min() to cap at 500px or 55vh, whichever is smaller */
/* This keeps the grid on screen without overflowing on shorter viewports */
.grid-container {
  width: min(500px, 55vh);
  height: min(500px, 55vh);
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  grid-template-rows: 1fr 1fr 1fr;
  background-color: #aa336a;
  border: #aa336a 5px solid;
  border-radius: 3%;
}

/* Each group of buttons (mode, difficulty, marker) stacks vertically in the sidebar */
.mode-toggle {
  display: flex;
  flex-direction: column;
  gap: 8px;
  width: 100%;
}

/* Base button style: transparent with a pink border */
.mode-btn {
  width: 100%;
  padding: 8px 16px;
  font-size: 0.95rem;
  border: 2px solid #aa336a;
  border-radius: 8px;
  background-color: transparent;
  color: #aa336a;
  cursor: pointer;
  text-align: center;
  -webkit-appearance: none;
  appearance: none;
  outline: none;
}

/* Active state: filled pink background, white text */
.mode-btn--active {
  background-color: #aa336a;
  color: #ffffff;
}

/* hidden must come after any display rules to win the specificity battle */
.hidden {
  display: none;
}

/* difficulty-controls needs display:flex when visible */
/* Declared separately from :not(.hidden) to avoid specificity conflicts */
#difficulty-controls {
  display: flex;
  flex-direction: column;
  gap: 16px;
  width: 100%;
}

/* Explicit override so .hidden wins over the display:flex above */
#difficulty-controls.hidden {
  display: none;
}

/* Each square fills its grid cell and centres its text content */
/* font-size scales with viewport height so X and O stay proportional to the grid */
.square {
  height: 100%;
  width: 100%;
  border: #000000 5px solid;
  display: flex;
  justify-content: center;
  align-items: center;
  border-radius: 10%;
  background-color: #f0f8ff;
  font-size: clamp(20px, 8vh, 125px);
  font-weight: bold;
  cursor: pointer;
}

/* Win highlight: green background on the three winning squares */
.square--winner {
  background-color: #008000;
}

/* Draw highlight: brown background on all squares when no winner */
.square--draw {
  background-color: #a52a2a;
}

.reset-button {
  padding: 0 20px;
  height: 40px;
  background-color: #fdfd96;
  color: #000000;
  border-radius: 8px;
  font-size: 1rem;
  cursor: pointer;
}

/* Flashing animation on the message box after a win or draw */
.winner {
  animation: flashing 2s linear infinite;
}

@keyframes flashing {
  0% {
    opacity: 0;
  }
  10% {
    opacity: 0.7;
  }
  50% {
    opacity: 1;
  }
  90% {
    opacity: 0.7;
  }
  100% {
    opacity: 0;
  }
}

/* Mobile: stack controls above grid, grid fills the available width */
/* order properties resequence elements without changing the HTML */
@media (max-width: 600px) {
  .game-layout {
    flex-direction: column;
    align-items: center;
    width: 100%;
  }

  /* Controls sit above the grid on mobile */
  .mode-controls {
    width: 100%;
    height: auto;
    justify-content: flex-start;
    order: 1;
  }

  /* Grid follows the controls */
  .section-container {
    order: 2;
    width: 100%;
  }

  /* calc(100vw - 40px) accounts for the 20px padding on each side of main */
  .grid-container {
    width: min(calc(100vw - 40px), 55vh);
    height: min(calc(100vw - 40px), 55vh);
  }

  /* Button pairs sit side by side on mobile rather than stacking */
  .mode-toggle {
    flex-direction: row;
  }

  #difficulty-controls {
    width: 100%;
  }

  /* Reset button moves below the grid on mobile using order */
  .reset-button {
    width: 100%;
    order: 3;
    border: 2px solid #000000;
  }
}

/* Tablet portrait: sidebar and grid shrink to fit between 601px and 900px */
/* Prevents the side-by-side layout from overflowing at 768px (iPad Mini/Air portrait) */
@media (max-width: 900px) and (min-width: 601px) {
  /* Tighter gap between sidebar and grid at tablet size */
  .game-layout {
    gap: 16px;
  }

  /* Spacer narrows to match the smaller sidebar width */
  .game-layout::after {
    width: 120px;
  }

  /* Sidebar narrows and height matches the smaller grid */
  .mode-controls {
    width: 120px;
    height: min(400px, 55vh);
  }

  /* Grid caps at 400px instead of 500px to fit the available width */
  .grid-container {
    width: min(400px, 55vh);
    height: min(400px, 55vh);
  }
}