/* Modern CSS Reset & Design Tokens */
:root {
  --bg-gradient: radial-gradient(circle at 50% 20%, #1e293b, #0f172a, #020617);
  --card-bg: rgba(30, 41, 59, 0.7);
  --card-border: rgba(255, 255, 255, 0.1);
  --card-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5), 0 0 0 1px rgba(255, 255, 255, 0.05);
  
  --text-main: #f8fafc;
  --text-muted: #94a3b8;
  --text-dim: #64748b;

  --accent-color: #3b82f6;
  --accent-hover: #2563eb;
  --accent-focus: rgba(59, 130, 246, 0.4);

  --error-color: #ef4444;
  --error-bg: rgba(239, 68, 68, 0.15);
  --error-border: rgba(239, 68, 68, 0.4);

  --success-color: #22c55e;
  --success-bg: rgba(34, 197, 94, 0.15);
  --success-border: rgba(34, 197, 94, 0.4);

  --input-bg: rgba(15, 23, 42, 0.6);
  --input-border: rgba(148, 163, 184, 0.2);

  --radius-lg: 20px;
  --radius-md: 12px;
  --radius-full: 9999px;

  --transition-base: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg-gradient);
  color: var(--text-main);
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1.5rem;
  overflow-x: hidden;
}

/* Screen reader utility */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border-width: 0;
}

/* Layout Wrapper */
.page-wrapper {
  width: 100%;
  max-width: 420px;
  perspective: 1000px;
}

/* Card Styling */
.screen-card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  box-shadow: var(--card-shadow);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-radius: var(--radius-lg);
  padding: 2.5rem 2rem;
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
  transition: transform var(--transition-base), opacity var(--transition-base);
}

.screen-card.hidden {
  display: none;
  opacity: 0;
  transform: scale(0.95);
}

.screen-card.active {
  display: flex;
  opacity: 1;
  transform: scale(1);
  animation: cardFadeIn 0.4s ease-out forwards;
}

@keyframes cardFadeIn {
  from {
    opacity: 0;
    transform: translateY(16px) scale(0.96);
  }
  to {
    opacity: 1;
    transform: translateY(0) scale(1);
  }
}

/* Avatar Badge */
.avatar-badge {
  width: 68px;
  height: 68px;
  border-radius: var(--radius-full);
  background: rgba(59, 130, 246, 0.1);
  border: 1px solid rgba(59, 130, 246, 0.25);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 1.25rem;
  color: var(--accent-color);
  transition: all var(--transition-base);
}

.avatar-badge.success {
  background: var(--success-bg);
  border-color: var(--success-border);
  color: var(--success-color);
}

.icon {
  width: 28px;
  height: 28px;
  display: inline-block;
  vertical-align: middle;
}

/* Header */
.card-header {
  margin-bottom: 1.75rem;
}

.card-title {
  font-size: 1.5rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 0.35rem;
  color: var(--text-main);
}

.card-subtitle {
  font-size: 0.875rem;
  color: var(--text-muted);
  line-height: 1.4;
}

/* Form & Input */
.lock-form {
  width: 100%;
  display: flex;
  flex-direction: column;
  gap: 1.1rem;
}

.input-group {
  position: relative;
  display: flex;
  align-items: center;
  width: 100%;
}

.input-group input {
  width: 100%;
  padding: 0.875rem 3rem 0.875rem 1.1rem;
  font-size: 1rem;
  color: var(--text-main);
  background: var(--input-bg);
  border: 1px solid var(--input-border);
  border-radius: var(--radius-md);
  outline: none;
  transition: border-color var(--transition-base), box-shadow var(--transition-base);
  text-align: center;
  letter-spacing: 0.1em;
}

.input-group input::placeholder {
  letter-spacing: normal;
  color: var(--text-dim);
}

.input-group input:focus {
  border-color: var(--accent-color);
  box-shadow: 0 0 0 3px var(--accent-focus);
}

/* Error state on input */
.input-group.has-error input {
  border-color: var(--error-color);
  box-shadow: 0 0 0 3px var(--error-bg);
}

/* Toggle visibility button */
.toggle-btn {
  position: absolute;
  right: 0.75rem;
  background: transparent;
  border: none;
  color: var(--text-dim);
  cursor: pointer;
  padding: 0.35rem;
  border-radius: 6px;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: color var(--transition-base);
}

.toggle-btn:hover {
  color: var(--text-main);
}

.toggle-btn:focus-visible {
  outline: 2px solid var(--accent-color);
}

.toggle-btn .icon {
  width: 20px;
  height: 20px;
}

/* Submit Button */
.submit-btn {
  width: 100%;
  padding: 0.875rem 1.5rem;
  background: var(--accent-color);
  color: #ffffff;
  border: none;
  border-radius: var(--radius-md);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  transition: background-color var(--transition-base), transform 0.1s ease, box-shadow var(--transition-base);
  box-shadow: 0 4px 14px 0 rgba(59, 130, 246, 0.39);
}

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

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

.submit-btn:focus-visible {
  outline: 3px solid var(--accent-focus);
  outline-offset: 2px;
}

.btn-icon {
  width: 18px;
  height: 18px;
  transition: transform var(--transition-base);
}

.submit-btn:hover .btn-icon {
  transform: translateX(3px);
}

/* Feedback message */
.feedback-msg {
  min-height: 1.25rem;
  font-size: 0.875rem;
  font-weight: 500;
  transition: all var(--transition-base);
  opacity: 0;
  transform: translateY(-4px);
}

.feedback-msg.show-error {
  opacity: 1;
  transform: translateY(0);
  color: var(--error-color);
}

.feedback-msg.show-success {
  opacity: 1;
  transform: translateY(0);
  color: var(--success-color);
}

/* Demo hint */
.demo-hint {
  font-size: 0.8rem;
  color: var(--text-dim);
  margin-top: 0.5rem;
}

.demo-hint code {
  background: rgba(255, 255, 255, 0.08);
  padding: 0.15rem 0.4rem;
  border-radius: 4px;
  color: var(--text-muted);
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
}

/* Shake Animation */
.shake {
  animation: shakeAnimation 0.45s cubic-bezier(0.36, 0.07, 0.19, 0.97) both;
}

@keyframes shakeAnimation {
  10%, 90% {
    transform: translate3d(-2px, 0, 0);
  }
  20%, 80% {
    transform: translate3d(4px, 0, 0);
  }
  30%, 50%, 70% {
    transform: translate3d(-6px, 0, 0);
  }
  40%, 60% {
    transform: translate3d(6px, 0, 0);
  }
}

/* Unlocked screen content */
.unlocked-content {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
  width: 100%;
}

.unlocked-content p {
  color: var(--text-muted);
  font-size: 0.95rem;
}

.secondary-btn {
  width: 100%;
  padding: 0.75rem 1.5rem;
  background: transparent;
  color: var(--text-muted);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-md);
  font-size: 0.95rem;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition-base);
}

.secondary-btn:hover {
  background: rgba(255, 255, 255, 0.05);
  color: var(--text-main);
  border-color: rgba(255, 255, 255, 0.2);
}

.secondary-btn:focus-visible {
  outline: 2px solid var(--accent-color);
}