:root {
  --primary-color-start: #4F46E5; /* Indigo */
  --primary-color-end:   #8B5CF6; /* Violet */
  --background-color: #f8f9fc;
  --container-bg: #ffffff;
  --text-color: #1f2937;
  --label-color: #374151;
  --border-color: #d1d5db;
  --shadow-color: rgba(0, 0, 0, 0.08);
}

/* Base */
* { box-sizing: border-box; }
html, body {
  height: 100%;
  margin: 0;
  background: var(--background-color);
  color: var(--text-color);
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

/* Container */
.chat-container {
  max-width: 450px;
  margin: 40px auto;
  background: var(--container-bg);
  border-radius: 15px;
  border-top: 6px solid var(--primary-color-start);
  box-shadow: 0 4px 15px var(--shadow-color);
  padding: 30px;
}

/* Header */
.chat-header {
  display: flex;
  justify-content: center;
  margin-bottom: 18px;
}
#logo { height: 50px; object-fit: contain; }

/* Short input */
.input-area { margin-bottom: 14px; }
.input-area input {
  width: 100%;
  padding: 18px;
  border: 1px solid var(--border-color);
  border-radius: 8px;
  font-size: 17px;
  outline: none;
  background: #fff;
}
.input-area input:focus {
  border-color: var(--primary-color-start);
  box-shadow: 0 0 0 3px rgba(79,70,229,.15);
}

/* Options */
.options-stack { display: grid; gap: 12px; margin-bottom: 14px; }
.option-group {
  background: #fff;
  border: 1px solid var(--border-color);
  border-radius: 10px;
  padding: 10px;
}
.group-label {
  font-size: 13px;
  font-weight: 600;
  color: var(--label-color);
  margin-bottom: 6px;
}
.btn-row { display: flex; flex-wrap: wrap; gap: 8px; }

/* Buttons */
.btn {
  padding: 12px 14px;
  border-radius: 8px;
  border: 1px solid var(--border-color);
  background: #fff;
  color: var(--primary-color-start);
  font-weight: 700;
  font-size: 14px;
  cursor: pointer;
  transition: .2s ease;
}
.btn:hover,
.btn:focus {
  background: linear-gradient(90deg, var(--primary-color-start), var(--primary-color-end));
  color: #fff;
  outline: none;
}
.btn.primary {
  width: 100%;
  padding: 18px;
  font-size: 18px;
  background: linear-gradient(90deg, var(--primary-color-start), var(--primary-color-end));
  color: #fff;
  border: none;
}
.btn.primary:hover { opacity: .92; }
.btn.ghost { background: #fff; color: var(--primary-color-start); }
.toggle.selected {
  background: linear-gradient(90deg, var(--primary-color-start), var(--primary-color-end));
  color: #fff;
}

/* Composer */
.composer { display: grid; gap: 10px; margin-bottom: 14px; }
#long-input {
  width: 100%;
  padding: 16px;
  border: 1px solid var(--border-color);
  border-radius: 8px;
  resize: vertical;
  min-height: 120px;
  font-size: 16px;
  background: #fff;
  outline: none;
}
#long-input:focus {
  border-color: var(--primary-color-start);
  box-shadow: 0 0 0 3px rgba(79,70,229,.15);
}

/* Response area */
.chat-output {
  min-height: 160px;
  background: #f3f4f6;
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 20px;
  font-size: 16px;
  line-height: 1.6;
  color: var(--text-color);
  white-space: pre-wrap;
}

/* Footer */
.action-footer {
  margin-top: 12px;
  display: flex;
  justify-content: flex-end;
}
.hidden { display: none; }

/* Accessibility */
button:focus-visible, textarea:focus-visible, input:focus-visible {
  outline: 3px solid rgba(79,70,229,.35);
  outline-offset: 2px;
}

/* Mobile */
@media (max-width: 520px) {
  .chat-container { margin: 20px 12px; padding: 22px; }
}