:root {
  --bg-dark: #0f0f1a;
  --panel-bg: rgba(30, 30, 47, 0.7);
  --primary: #ff6347;
  --primary-glow: rgba(255, 99, 71, 0.4);
  --accent: #ffa07a;
  --success: #00e676;
  --error: #ff1744;
  --light-square: #e2e8f0;
  --dark-square: #4a5568;
}

body {
  font-family: 'Plus Jakarta Sans', sans-serif;
  background: radial-gradient(circle at center, #1e1e38 0%, var(--bg-dark) 100%);
  color: #ffffff;
  text-align: center;
  margin: 0;
  padding: 80px 20px 40px 20px;
  min-height: 100vh;
  box-sizing: border-box;
}

.project-back-button {
  position: fixed;
  left: 24px;
  top: 24px;
  padding: 10px 18px;
  border-radius: 12px;
  background: rgba(255, 255, 255, 0.1);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border: 1px solid rgba(255, 255, 255, 0.2);
  text-decoration: none;
  z-index: 9999;
  font-weight: 700;
  color: #ffffff;
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
  transition: all 0.3s ease;
}

.project-back-button:hover {
  background: #ffffff;
  color: var(--bg-dark);
  transform: translateY(-2px);
}

.container {
  max-width: fit-content;
  margin: 0 auto;
  padding: 35px;
  background: var(--panel-bg);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border: 1px solid rgba(255, 255, 255, 0.08);
  box-shadow: 0 16px 45px rgba(0, 0, 0, 0.6);
  border-radius: 24px;
  animation: fadeIn 0.6s ease-out;
}

h1 {
  font-size: 2.8em;
  font-weight: 800;
  background: linear-gradient(135deg, #ff8a75 0%, var(--primary) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  margin: 0 0 5px 0;
}

.subtitle {
  color: #a0aec0;
  font-size: 1rem;
  margin-bottom: 30px;
}

.board-details {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 25px;
  background: rgba(0, 0, 0, 0.2);
  padding: 15px 25px;
  border-radius: 16px;
  margin-bottom: 25px;
}

.board-size {
  display: flex;
  align-items: center;
  gap: 12px;
}

label {
  font-weight: 600;
  font-size: 1.05em;
  color: var(--accent);
}

input[type="number"] {
  padding: 10px;
  font-size: 1.1em;
  font-weight: 600;
  border: 2px solid rgba(255, 160, 122, 0.4);
  border-radius: 10px;
  width: 70px;
  text-align: center;
  background-color: #12121f;
  color: #ffffff;
  outline: none;
  transition: border-color 0.3s;
}

input[type="number"]:focus {
  border-color: var(--accent);
  box-shadow: 0 0 10px rgba(255, 160, 122, 0.2);
}

button {
  font-family: inherit;
  font-weight: 700;
  background: linear-gradient(135deg, #48bb78 0%, #38a169 100%);
  color: #fff;
  border: none;
  padding: 12px 26px;
  font-size: 1.1em;
  border-radius: 10px;
  cursor: pointer;
  box-shadow: 0 4px 12px rgba(56, 161, 105, 0.3);
  transition: all 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

button:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(72, 187, 120, 0.4);
}

.reset-button {
  background: linear-gradient(135deg, #ff6347 0%, #e53e3e 100%);
  box-shadow: 0 4px 12px rgba(229, 62, 62, 0.3);
}

.reset-button:hover {
  box-shadow: 0 6px 20px rgba(255, 99, 71, 0.4);
}

#gameBoard {
  display: grid;
  margin: 25px auto;
  border: 6px solid #1a1a2e;
  background: #1a1a2e;
  border-radius: 14px;
  width: fit-content;      
  max-width: 95vw;        
  max-height: 65vh;       
  overflow: auto;         
  padding: 4px;
  box-shadow: inset 0 4px 20px rgba(0,0,0,0.5);
}

.square {
  width: 55px;
  height: 55px;
  display: flex;
  justify-content: center;
  align-items: center;
  cursor: pointer;
  position: relative;
  transition: background-color 0.2s, transform 0.1s;
}

/* Perfect Chessboard colors applied dynamically via JS classes */
.square.light-tile { background-color: var(--light-square); }
.square.dark-tile { background-color: var(--dark-square); }

/* Track View Hover Guidance Lines */
.square.guideline::after {
  content: '';
  position: absolute;
  inset: 0;
  background-color: rgba(255, 160, 122, 0.15);
  pointer-events: none;
}

.square:hover {
  filter: brightness(1.15);
}

.queen {
  font-size: 34px;
  color: #1a1a2e;
  pointer-events: none;
  z-index: 2;
  animation: dropIn 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275) forwards;
}

#message {
  font-size: 1.25em;
  font-weight: 700;
  margin: 15px 0;
  min-height: 30px;
  color: var(--success);
  text-shadow: 0 2px 8px rgba(0, 230, 118, 0.2);
}

#message.error {
  color: var(--error);
  text-shadow: 0 2px 8px rgba(255, 23, 68, 0.2);
}

.highlight {
  background-color: var(--error) !important;
  animation: shake 0.4s ease-in-out;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(20px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes dropIn {
  from { opacity: 0; transform: scale(0.3) rotate(-15deg); }
  to { opacity: 1; transform: scale(1) rotate(0deg); }
}

@keyframes shake {
  0%, 100% { transform: translateX(0); }
  25% { transform: translateX(-4px); }
  75% { transform: translateX(4px); }
}