/* Visually hidden class for screen readers */
.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: -1px;
  padding: 0;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  border: 0;
}

/* Define font styles with fallbacks to prevent layout shifts */
@font-face {
  font-family: 'Poppins';
  src: url('https://fonts.googleapis.com/css2?family=Poppins:wght@300;400;500;600;700&display=swap');
  font-display: swap;
}

@font-face {
  font-family: 'Roboto';
  src: url('https://fonts.googleapis.com/css2?family=Roboto:wght@300;400;500;700&display=swap');
  font-display: swap;
}


/* Optimized non-critical CSS with unused rules removed */
:root {
  --primary: #1a2a3a; /* Darkened for better contrast */
  --secondary: #1e8449; /* Darkened for better contrast */
  --accent: #c0392b; /* Adjusted for better contrast */
  --bg: #f5f7f8; /* Lightened background */
  --card-bg: #fff;
  --text: #222831; /* Darker text color for better contrast */
  --gradient: linear-gradient(135deg, #1a2a3a, #34495e);
}

/* High-performance transitions only on interactive elements */
.toggle-slider, button, .file-upload label, .notification {
  transition: transform 0.3s ease, background-color 0.3s ease, box-shadow 0.3s ease;
}

/* Labels and form elements */
.area label {
  font-weight: 600;
  margin-bottom: 10px;
  display: flex;
  align-items: center;
  gap: 8px;
  color: #1a2a3a; /* Using darker color for better contrast */
}

.mode-toggle button {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.9rem;
}

.mode-toggle.file-active .slider {
  transform: translateX(calc(100% + 5px));
}

/* Tooltips */
.info-container {
  position: relative;
  display: inline-block;
  cursor: pointer;
}

.info-tooltip {
  position: absolute;
  top: 50%;
  left: 110%;
  transform: translateY(-50%);
  background: #222; /* Darker background for better contrast */
  color: #fff;
  font-size: 0.75rem;
  padding: 5px 10px;
  border-radius: 6px;
  white-space: nowrap;
  opacity: 0;
  pointer-events: none;
  box-shadow: 0 3px 10px rgba(0,0,0,0.2);
  font-weight: 500; /* Increased font weight for better readability */
  transition: opacity 0.2s ease;
}

.info-tooltip.show { opacity: 1; }

/* Form styling */
textarea:focus, input[type="text"]:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(0,0,0,0.05);
}

.counter {
  text-align: right;
  font-size: 0.8rem;
  color: rgba(0,0,0,0.7); /* Improved contrast from 0.5 to 0.7 */
  margin-top: 5px;
}

/* Toggle switches */
.toggle-container {
  margin: 15px 0;
  display: flex;
  align-items: center;
  gap: 10px;
}

.toggle-label {
  display: flex;
  align-items: center;
  gap: 10px;
  cursor: pointer;
}

.toggle {
  position: relative;
  display: inline-block;
  width: 50px;
  height: 28px;
}

.toggle input { 
  opacity: 0;
  width: 0;
  height: 0;
}

.toggle-slider {
  position: absolute;
  cursor: pointer;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: rgba(0,0,0,0.2);
  border-radius: 34px;
}

.toggle-slider:before {
  position: absolute;
  content: "";
  height: 20px;
  width: 20px;
  left: 4px;
  bottom: 4px;
  background-color: white;
  border-radius: 50%;
}

input:checked + .toggle-slider {
  background-color: var(--primary);
}

input:checked + .toggle-slider:before {
  transform: translateX(22px);
}

.toggle-label {
  font-weight: 500;
  font-size: 0.95rem;
  color: #333; /* Added specific color to ensure contrast */
}

.secret-key-field {
  margin-bottom: 20px;
  display: none;
  background: rgba(0,0,0,0.02);
  padding: 15px;
  border-radius: 10px;
  box-shadow: inset 0 1px 3px rgba(0,0,0,0.1);
}

.aes-option { 
  margin-top: 15px;
}

/* Button interactions */
.process-buttons button:hover { 
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(0,0,0,0.15);
}

.process-buttons button:active {
  transform: translateY(0);
  box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

/* Output area */
.output-container {
  display: flex;
  gap: 15px;
  align-items: flex-start;
}

.button-panel {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.button-panel button {
  padding: 12px;
  border: none;
  border-radius: 8px;
  font-size: 0.9rem;
  font-weight: 600;
  color: #fff;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  box-shadow: 0 3px 10px rgba(0,0,0,0.1);
}

.button-panel button:hover { 
  transform: translateY(-2px);
  box-shadow: 0 5px 15px rgba(0,0,0,0.15);
}

.btn-copy { 
  background: var(--primary);
}

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

/* File section */
#fileSection {
  display: none;
}

.file-upload {
  margin: 20px 0;
  display: flex;
  flex-direction: column;
  gap: 15px;
}

.file-upload label {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 30px;
  border: 2px dashed rgba(0,0,0,0.1);
  border-radius: 12px;
  cursor: pointer;
  background: rgba(0,0,0,0.02);
  min-height: 200px;
  width: 100%;
  aspect-ratio: 16/9;
}

.file-upload label i {
  font-size: 3rem;
  color: var(--primary);
  margin-bottom: 15px;
  opacity: 0.8;
}

.file-upload label p {
  font-weight: 500;
  color: var(--text);
  opacity: 1; /* Increased from 0.8 to 1 for better contrast */
}

.file-upload label:hover {
  border-color: var(--primary);
  transform: translateY(-2px);
  box-shadow: 0 5px 15px rgba(0,0,0,0.05);
}

.file-upload label:hover i {
  transform: scale(1.1);
  opacity: 1;
}

.file-upload input[type="file"] {
  display: none;
}

.file-info {
  margin-top: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  font-weight: 600; /* Increased font weight */
  color: #222; /* Added explicit color */
  background: rgba(0,0,0,0.05); /* Slightly darker background */
  padding: 10px 15px;
  border-radius: 8px;
}

.download-button {
  padding: 12px 25px;
  background: var(--secondary);
  color: white;
  border: none;
  border-radius: 10px;
  font-weight: 600;
  cursor: pointer;
  margin: 20px auto;
  display: none;
  box-shadow: 0 4px 15px rgba(0,0,0,0.1);
}

.download-button:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(0,0,0,0.15);
}

footer {
  text-align: center;
  font-size: 0.85rem;
  color: rgba(0,0,0,0.8); /* Improved from 0.6 to 0.8 for better contrast */
  margin-top: 20px;
  padding: 15px;
  background: rgba(255,255,255,0.5); /* Enhanced background opacity for better contrast */
  border-radius: 10px;
  width: 100%;
  max-width: 800px;
}

/* Load animations only if user prefers them and after critical content loads */
@media (prefers-reduced-motion: no-preference) {
  .js-animations-loaded .process-buttons button {
    background-size: 200% 200%;
    animation: gradientFlow 5s ease infinite;
  }

  .js-animations-loaded .download-button {
    animation: pulse 2s infinite;
  }

  @keyframes gradientFlow {
    0% { background-position: 0% 50%; }
    50% { background-position: 100% 50%; }
    100% { background-position: 0% 50%; }
  }

  @keyframes pulse {
    0% { box-shadow: 0 0 0 0 rgba(39, 174, 96, 0.4); }
    70% { box-shadow: 0 0 0 10px rgba(39, 174, 96, 0); }
    100% { box-shadow: 0 0 0 0 rgba(39, 174, 96, 0); }
  }
}

/* Critical rendering optimizations */
textarea, input[type="text"] {
  will-change: contents; /* Hint to browser for optimization */
  content-visibility: auto;
  contain-intrinsic-size: auto 150px;
}

.area {
  display: block;
  content-visibility: auto;
  contain-intrinsic-size: auto 200px;
}

body {
  background-color: var(--bg);
  color: var(--text);
  display: flex;
  flex-direction: column;
  align-items: center;
  min-height: 100vh;
  padding: 20px;
  line-height: 1.6;
}

header, main, footer {
  width: 100%;
  max-width: 800px;
}

header {
  background: var(--gradient);
  color: #fff;
  padding: 15px 20px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-radius: 15px 15px 0 0;
  box-shadow: 0 4px 15px rgba(0,0,0,0.1);
  position: relative;
  overflow: hidden;
}

header h1 { 
  font-size: 1.8rem; 
  position: relative;
  z-index: 1;
  text-shadow: 0 2px 5px rgba(0,0,0,0.2);
}

main {
  background: var(--card-bg);
  padding: 25px;
  border-radius: 0 0 15px 15px;
  box-shadow: 0 8px 25px rgba(0,0,0,0.1);
  position: relative;
}


.mode-toggle {
  display: flex;
  background: rgba(0,0,0,0.05);
  border-radius: 12px;
  padding: 5px;
  margin: 0 auto 25px;
  width: fit-content;
  position: relative;
}

.mode-toggle .slider {
  position: absolute;
  top: 5px;
  left: 5px;
  background: var(--primary);
  border-radius: 8px;
  width: calc(50% - 5px);
  height: calc(100% - 10px);
  transition: all 0.3s cubic-bezier(0.68, -0.55, 0.27, 1.55);
}

.area {
  margin-bottom: 20px;
  position: relative;
  background: rgba(0,0,0,0.02);
  padding: 20px;
  border-radius: 12px;
  box-shadow: 0 3px 10px rgba(0,0,0,0.05);
  min-height: 120px;
  width: 100%;
  content-visibility: auto;
  contain-intrinsic-size: 1px 120px;
}

textarea, input[type="text"] {
  width: 100%;
  padding: 12px 15px;
  border: 2px solid rgba(0,0,0,0.2); /* Darker border for better visibility */
  border-radius: 10px;
  font-size: 0.95rem;
  background: rgba(255,255,255,0.9); /* Higher opacity background */
  color: #222; /* Explicitly dark text for maximum contrast */
  min-height: 60px;
  aspect-ratio: auto;
  box-sizing: border-box;
}

textarea {
  min-height: 120px;
  height: calc(1.6em * 6);
}

.process-buttons {
  display: flex;
  gap: 15px;
  justify-content: center;
  margin-bottom: 25px;
}

.process-buttons button {
  padding: 12px 25px;
  border: none;
  border-radius: 10px;
  font-size: 1rem;
  font-weight: 600;
  color: #fff;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 10px;
  box-shadow: 0 4px 15px rgba(0,0,0,0.1);
}

.btn-encrypt { 
  background: var(--primary);
  font-weight: 700; /* Bolder text for better readability */
}

.btn-decrypt { 
  background: var(--secondary);
  font-weight: 700; /* Bolder text for better readability */
}

.notification {
  position: fixed;
  bottom: -100px;
  left: 50%;
  transform: translateX(-50%);
  background-color: var(--secondary);
  color: white;
  padding: 12px 25px;
  border-radius: 10px;
  box-shadow: 0 4px 15px rgba(0,0,0,0.2);
  display: flex;
  align-items: center;
  gap: 10px;
  z-index: 1000;
  transition: transform 0.3s ease, opacity 0.3s ease;
  opacity: 0;
  width: 300px;
  height: 60px;
  transform: translateX(-50%) translateY(100px);
  pointer-events: none;
}

.notification.show {
  opacity: 1;
  transform: translateX(-50%) translateY(-100px);
  pointer-events: auto;
}