:root {
  --bg: #0f1117;
  --card: #161b22;
  --border: #2a2f3a;
  --text: #e6edf3;
  --muted: #8b949e;
  --accent: #4c8bf5;
  --accent-hover: #3a6fd8;
  --input-bg: #0d1117;
  --error: #f85149;
  --success: #3fb950;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  padding: 20px;
}

.container {
  max-width: 900px;
  margin: 0 auto;
}

/* === HEADER === */
.header {
  text-align: center;
  margin-bottom: 40px;
  padding-bottom: 20px;
  border-bottom: 1px solid var(--border);
}

.header h1 {
  margin: 0 0 10px 0;
  font-size: 32px;
  letter-spacing: 3px;
  font-weight: 600;
}

/* === TODAY'S CODES SECTION === */
.today-section {
  margin-bottom: 40px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 24px;
}

.section-title {
  margin: 0 0 20px 0;
  font-size: 16px;
  font-weight: 600;
  color: var(--text);
  letter-spacing: 1px;
  text-transform: uppercase;
}

.section-title.date-display {
  text-transform: none;
  font-size: 15px;
  font-weight: 400;
  color: var(--muted);
  letter-spacing: 0.5px;
}

.codes-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
}

.code-card {
  background: var(--input-bg);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 20px;
  text-align: center;
  transition: all 0.2s ease;
}

.code-card:hover {
  border-color: var(--accent);
  background: rgba(76, 139, 245, 0.05);
}

.code-label {
  font-size: 11px;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-bottom: 12px;
}

.code-value {
  font-family: 'SFMono-Regular', 'Menlo', 'Monaco', monospace;
  font-size: 24px;
  letter-spacing: 2px;
  font-weight: 600;
  margin-bottom: 12px;
  color: var(--accent);
}

.copy-btn {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text);
  padding: 6px 12px;
  border-radius: 6px;
  font-size: 12px;
  cursor: pointer;
  transition: all 0.2s ease;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.copy-btn:hover {
  border-color: var(--accent);
  color: var(--accent);
}

.copy-btn:active {
  background: var(--accent);
  color: white;
}

/* === DIVIDER === */
.divider {
  height: 1px;
  background: var(--border);
  margin: 40px 0;
}

/* === CONVERTER SECTIONS === */
.converter-section {
  margin-bottom: 40px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 24px;
}

.converter-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
}

.converter-block {
  display: flex;
  flex-direction: column;
}

.block-title {
  margin: 0 0 16px 0;
  font-size: 14px;
  font-weight: 600;
  color: var(--text);
  letter-spacing: 0.5px;
}

.input-group {
  display: flex;
  gap: 10px;
  margin-bottom: 16px;
}

input[type="date"],
input[type="month"],
input[type="text"].code-input {
  flex: 1;
  padding: 12px;
  background: var(--input-bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text);
  font-size: 14px;
  font-family: system-ui, -apple-system, sans-serif;
  transition: all 0.2s ease;
}

input[type="date"],
input[type="month"] {
  color-scheme: dark;
}

input[type="date"]:focus,
input[type="month"]:focus,
input[type="text"].code-input:focus {
  outline: none;
  border-color: var(--accent);
  background: rgba(76, 139, 245, 0.08);
}

input[type="text"].code-input {
  text-transform: uppercase;
  letter-spacing: 2px;
  font-weight: 600;
  font-size: 16px;
  font-family: 'SFMono-Regular', 'Menlo', 'Monaco', monospace;
}

input[type="text"].code-input.invalid {
  border-color: var(--error);
  background: rgba(248, 81, 73, 0.08);
}

.action-btn {
  padding: 12px 20px;
  background: var(--accent);
  border: none;
  border-radius: 8px;
  color: white;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s ease;
  white-space: nowrap;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.action-btn:hover {
  background: var(--accent-hover);
}

.action-btn:active {
  transform: scale(0.98);
}

.action-btn:disabled {
  background: var(--muted);
  cursor: not-allowed;
  opacity: 0.6;
}

.result-card {
  background: var(--input-bg);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 16px;
  text-align: center;
  margin-top: 8px;
}

.result-value {
  font-family: 'SFMono-Regular', 'Menlo', 'Monaco', monospace;
  font-size: 20px;
  letter-spacing: 2px;
  font-weight: 600;
  color: var(--accent);
  margin-bottom: 8px;
}

.result-label {
  font-size: 11px;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-bottom: 8px;
}

.error-message {
  font-size: 12px;
  color: var(--error);
  margin-top: 8px;
  padding: 8px;
  background: rgba(248, 81, 73, 0.1);
  border: 1px solid rgba(248, 81, 73, 0.3);
  border-radius: 6px;
  text-align: center;
}

/* === FOOTER === */
.footer {
  text-align: center;
  padding-top: 20px;
  border-top: 1px solid var(--border);
  color: var(--muted);
  font-size: 12px;
  margin-top: 40px;
}

.footer p {
  margin: 0;
}

/* === RESPONSIVE: TABLET (640px+) === */
@media (max-width: 767px) {
  .codes-grid {
    grid-template-columns: 1fr;
  }

  .converter-row {
    grid-template-columns: 1fr;
    gap: 32px;
  }

  .header h1 {
    font-size: 28px;
  }

  .input-group {
    flex-direction: column;
  }

  .action-btn {
    width: 100%;
  }
}

/* === RESPONSIVE: MOBILE (<640px) === */
@media (max-width: 639px) {
  body {
    padding: 16px;
  }

  .container {
    margin: 0 auto;
  }

  .header {
    margin-bottom: 32px;
    padding-bottom: 16px;
  }

  .header h1 {
    font-size: 24px;
    letter-spacing: 2px;
  }

  .today-section,
  .converter-section {
    padding: 16px;
    border-radius: 10px;
  }

  .codes-grid {
    grid-template-columns: 1fr;
    gap: 12px;
  }

  .code-card {
    padding: 16px;
  }

  .code-value {
    font-size: 24px;
    letter-spacing: 2px;
  }

  .converter-row {
    grid-template-columns: 1fr;
    gap: 28px;
  }

  .input-group {
    flex-direction: column;
    gap: 8px;
  }

  .action-btn {
    width: 100%;
    padding: 14px;
  }

  .section-title {
    font-size: 14px;
    margin-bottom: 16px;
  }

  .block-title {
    font-size: 13px;
  }

  .divider {
    margin: 32px 0;
  }
}