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

:root {
  --bg: #0f1117;
  --surface: #1a1d2e;
  --surface2: #252840;
  --border: #2e3250;
  --accent: #6c63ff;
  --accent-hover: #5a52e0;
  --text: #e8e8f0;
  --text-muted: #7a7d9a;
  --success: #4ade80;
  --danger: #f87171;
  --timer-bg: #2e3250;
}

.hidden { display: none !important; }

body {
  background: var(--bg);
  color: var(--text);
  font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
  min-height: 100vh;
  display: flex;
  align-items: flex-start;
  justify-content: center;
  padding: 48px 16px;
}

.container {
  width: 100%;
  max-width: 460px;
  display: flex;
  flex-direction: column;
  gap: 24px;
}

.header { text-align: center; }

.logo {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--accent);
  letter-spacing: -0.5px;
}

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 20px;
}

.input-group {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

input[type="text"] {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 10px;
  color: var(--text);
  font-size: 0.95rem;
  padding: 13px 15px;
  outline: none;
  transition: border-color 0.2s;
  width: 100%;
  letter-spacing: 0.5px;
}

input[type="text"]::placeholder {
  color: var(--text-muted);
  letter-spacing: 0;
}

input[type="text"]:focus { border-color: var(--accent); }

#genBtn {
  background: var(--accent);
  border: none;
  border-radius: 10px;
  color: #fff;
  cursor: pointer;
  font-size: 0.95rem;
  font-weight: 600;
  padding: 13px 20px;
  transition: background 0.2s, transform 0.1s;
  width: 100%;
}

#genBtn:hover { background: var(--accent-hover); }
#genBtn:active { transform: scale(0.98); }

.result-box {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 28px 24px 24px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 16px;
  animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to   { opacity: 1; transform: translateY(0); }
}

.otp-label {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1.5px;
  color: var(--text-muted);
}

.otp-code {
  font-size: 3rem;
  font-weight: 800;
  letter-spacing: 6px;
  color: var(--text);
  font-variant-numeric: tabular-nums;
  transition: color 0.3s;
  user-select: all;
  padding-left: 6px;
}

.otp-code.expiring { color: var(--danger); }

.timer-row {
  display: flex;
  align-items: center;
  gap: 10px;
  width: 100%;
}

.progress-wrap {
  flex: 1;
  height: 5px;
  background: var(--timer-bg);
  border-radius: 99px;
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: var(--accent);
  border-radius: 99px;
  transition: width 0.5s linear, background 0.5s;
}

.progress-fill.expiring { background: var(--danger); }

.timer-text {
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--text-muted);
  min-width: 28px;
  text-align: right;
}

.copy-btn {
  background: var(--accent);
  border: 1px solid var(--accent);
  border-radius: 10px;
  color: #fff;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 7px;
  font-size: 0.88rem;
  font-weight: 600;
  padding: 11px 24px;
  width: 100%;
  transition: all 0.2s;
}

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

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

.copy-btn.copied {
  background: var(--success);
  border-color: var(--success);
  color: #000;
}

.toast {
  position: fixed;
  bottom: 24px;
  left: 50%;
  transform: translateX(-50%) translateY(80px);
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: 12px;
  color: var(--text);
  font-size: 0.85rem;
  font-weight: 600;
  padding: 12px 20px;
  opacity: 0;
  transition: all 0.3s ease;
  pointer-events: none;
  z-index: 999;
  white-space: nowrap;
}

.toast.show { opacity: 1; transform: translateX(-50%) translateY(0); }
.toast.success { border-color: var(--success); color: var(--success); }
.toast.error { border-color: var(--danger); color: var(--danger); }

@media (max-width: 480px) {
  .otp-code { font-size: 2.2rem; letter-spacing: 8px; }
}