/* ===== Design Tokens ===== */
:root {
  --bg: #fafaf9;
  --surface: #ffffff;
  --text-primary: #0f172a;
  --text-secondary: #64748b;
  --border: #e2e8f0;
  --primary: #2563eb;
  --primary-hover: #1d4ed8;
  --primary-active: #1e40af;
  --error-bg: #fef2f2;
  --error-border: #fecaca;
  --error-text: #b91c1c;
  --radius-card: 12px;
  --radius-input: 8px;
  --radius-btn: 8px;
  --shadow-card: 0 1px 3px rgba(0,0,0,.06), 0 1px 2px rgba(0,0,0,.04);
  --shadow-hover: 0 4px 12px rgba(0,0,0,.08);
  --transition: 150ms ease-in-out;
}

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

/* ===== Base ===== */
body {
  font-family: 'Noto Sans SC', 'PingFang SC', 'Microsoft YaHei', system-ui, sans-serif;
  font-size: 16px;
  line-height: 1.5;
  color: var(--text-primary);
  background: var(--bg);
  min-height: 100vh;
  padding: 24px 16px;
  -webkit-font-smoothing: antialiased;
}

/* ===== Container ===== */
.container {
  max-width: 560px;
  margin: 0 auto;
  background: var(--surface);
  border-radius: var(--radius-card);
  padding: 32px 24px;
  box-shadow: var(--shadow-card);
}

/* ===== Typography ===== */
h1 {
  font-size: 24px;
  font-weight: 700;
  line-height: 1.25;
  color: var(--text-primary);
  margin-bottom: 8px;
}

.subtitle {
  font-size: 14px;
  color: var(--text-secondary);
  margin-bottom: 32px;
  line-height: 1.5;
}

label {
  display: block;
  font-size: 14px;
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: 8px;
  letter-spacing: 0.01em;
}

/* ===== Form ===== */
.input-section {
  margin-bottom: 16px;
}

textarea {
  width: 100%;
  border: 1.5px solid var(--border);
  border-radius: var(--radius-input);
  padding: 12px 16px;
  font-size: 15px;
  font-family: inherit;
  line-height: 1.6;
  color: var(--text-primary);
  background: var(--surface);
  resize: vertical;
  min-height: 120px;
  transition: border-color var(--transition), box-shadow var(--transition);
}

textarea::placeholder {
  color: #94a3b8;
  font-size: 14px;
}

textarea:hover {
  border-color: #94a3b8;
}

textarea:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(37,99,235,.12);
}

/* ===== Divider ===== */
.divider {
  display: flex;
  align-items: center;
  gap: 12px;
  color: var(--text-secondary);
  font-size: 13px;
  margin: 16px 0;
}

.divider::before,
.divider::after {
  content: '';
  flex: 1;
  height: 1px;
  background: var(--border);
}

/* ===== Upload Area ===== */
.upload-area {
  border: 1.5px dashed var(--border);
  border-radius: var(--radius-input);
  padding: 24px 16px;
  text-align: center;
  background: var(--bg);
  transition: border-color var(--transition), background var(--transition);
}

.upload-area:hover {
  border-color: #94a3b8;
  background: #f1f5f9;
}

.upload-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: var(--surface);
  border: 1.5px solid var(--border);
  border-radius: 6px;
  padding: 8px 16px;
  font-size: 14px;
  font-weight: 500;
  font-family: inherit;
  color: var(--text-primary);
  cursor: pointer;
  min-height: 36px;
  transition: background var(--transition), border-color var(--transition), transform var(--transition);
}

.upload-btn:hover {
  background: #f1f5f9;
  border-color: #94a3b8;
}

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

.upload-hint {
  margin-top: 8px;
  font-size: 12px;
  color: var(--text-secondary);
}

.preview-image {
  max-width: 100%;
  max-height: 180px;
  margin-top: 16px;
  border-radius: 8px;
  display: none;
  box-shadow: var(--shadow-card);
}

/* ===== Generate Button ===== */
.generate-btn {
  width: 100%;
  margin-top: 24px;
  padding: 0 24px;
  height: 48px;
  background: var(--primary);
  color: #fff;
  border: none;
  border-radius: var(--radius-btn);
  font-size: 15px;
  font-weight: 600;
  font-family: inherit;
  cursor: pointer;
  letter-spacing: 0.01em;
  transition: background var(--transition), transform var(--transition), box-shadow var(--transition);
}

.generate-btn:hover:not(:disabled) {
  background: var(--primary-hover);
  box-shadow: var(--shadow-hover);
}

.generate-btn:active:not(:disabled) {
  background: var(--primary-active);
  transform: scale(0.99);
}

.generate-btn:focus-visible {
  outline: 3px solid rgba(37,99,235,.4);
  outline-offset: 2px;
}

.generate-btn:disabled {
  background: #94a3b8;
  cursor: not-allowed;
  transform: none;
}

/* ===== Loading ===== */
.loading {
  display: none;
  text-align: center;
  padding: 32px 0 16px;
  color: var(--text-secondary);
  font-size: 14px;
}

.spinner {
  width: 28px;
  height: 28px;
  border: 2.5px solid var(--border);
  border-top-color: var(--primary);
  border-radius: 50%;
  animation: spin 0.7s linear infinite;
  margin: 0 auto 12px;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

/* ===== Result ===== */
.result {
  display: none;
  margin-top: 32px;
}

.result h2 {
  font-size: 14px;
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: 12px;
  letter-spacing: 0.02em;
  text-transform: uppercase;
}

.svg-container {
  border: 1px solid var(--border);
  border-radius: var(--radius-input);
  overflow: hidden;
  background: var(--surface);
}

.svg-container svg {
  display: block;
  width: 100%;
  height: auto;
}

/* ===== Download Button ===== */
.download-btn {
  width: 100%;
  margin-top: 12px;
  padding: 0 24px;
  height: 48px;
  background: var(--text-primary);
  color: #fff;
  border: none;
  border-radius: var(--radius-btn);
  font-size: 15px;
  font-weight: 600;
  font-family: inherit;
  cursor: pointer;
  transition: background var(--transition), transform var(--transition);
}

.download-btn:hover {
  background: #1e293b;
}

.download-btn:active {
  transform: scale(0.99);
}

.download-btn:focus-visible {
  outline: 3px solid rgba(15,23,42,.3);
  outline-offset: 2px;
}

/* ===== Error ===== */
.error {
  display: none;
  margin-top: 16px;
  padding: 12px 16px;
  background: var(--error-bg);
  border: 1px solid var(--error-border);
  border-radius: var(--radius-input);
  color: var(--error-text);
  font-size: 14px;
  line-height: 1.5;
}

/* ===== Mobile ===== */
@media (max-width: 480px) {
  body {
    padding: 0;
  }

  .container {
    border-radius: 0;
    min-height: 100vh;
    box-shadow: none;
    padding: 24px 16px;
  }
}