:root {
  --bg-color: #f0f2f5;
  --text-color: #1c1e21;
  --card-bg: #ffffff;
  --border-color: #dddfe2;
  --button-bg: #1877f2;
  --button-text: #ffffff;
  --input-bg: #ffffff;
  --nav-bg: #ffffff;
  --footer-bg: #ffffff;
}

[data-theme='dark'] {
  --bg-color: #18191a;
  --text-color: #e4e6eb;
  --card-bg: #242526;
  --border-color: #3e4042;
  --button-bg: #2d88ff;
  --button-text: #ffffff;
  --input-bg: #3a3b3c;
  --nav-bg: #242526;
  --footer-bg: #242526;
}

body {
  background-color: var(--bg-color);
  color: var(--text-color);
  transition: background-color 0.3s, color 0.3s;
  font-family: 'Pretendard', -apple-system, BlinkMacSystemFont, system-ui, Roboto, sans-serif;
  margin: 0;
  padding: 0;
  line-height: 1.6;
}

/* Navbar */
.navbar {
  position: sticky;
  top: 0;
  background-color: var(--nav-bg);
  border-bottom: 1px solid var(--border-color);
  z-index: 1000;
  padding: 0.5rem 0;
}

.nav-container {
  max-width: 1000px;
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0 20px;
}

.nav-logo {
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--button-bg);
  text-decoration: none;
}

.nav-menu {
  list-style: none;
  display: flex;
  align-items: center;
  gap: 20px;
  margin: 0;
  padding: 0;
}

.nav-menu a {
  text-decoration: none;
  color: var(--text-color);
  font-weight: 600;
  font-size: 0.9rem;
  transition: color 0.2s;
}

.nav-menu a:hover {
  color: var(--button-bg);
}

.theme-btn {
  padding: 6px 12px;
  font-size: 0.8rem;
}

/* Container */
.container {
  width: 100%;
  max-width: 800px;
  margin: 0 auto;
  padding: 40px 20px;
  box-sizing: border-box;
}

.hero-section {
  text-align: center;
  margin-bottom: 40px;
}

.hero-section h1 {
  font-size: 2.5rem;
  margin-bottom: 10px;
}

.card {
  background-color: var(--card-bg);
  padding: 30px;
  border-radius: 12px;
  box-shadow: 0 1px 2px rgba(0, 0, 0, 0.1);
  border: 1px solid var(--border-color);
  margin-bottom: 30px;
}

h2 {
  margin-top: 0;
  margin-bottom: 20px;
  border-left: 5px solid var(--button-bg);
  padding-left: 15px;
  text-align: left;
}

.description {
  margin-bottom: 20px;
  opacity: 0.9;
}

/* Test Section */
.upload-container {
  margin: 30px 0;
}

#image-upload { display: none; }

.upload-label {
  display: inline-block;
  padding: 15px 30px;
  background-color: #28a745;
  color: white;
  border-radius: 8px;
  cursor: pointer;
  font-weight: 700;
  font-size: 1.1rem;
}

#image-preview-container {
  margin: 20px auto;
  border-radius: 12px;
  overflow: hidden;
  max-width: 400px;
  border: 1px solid var(--border-color);
}

#image-preview { width: 100%; height: auto; display: block; }

/* Info List */
.info-list {
  padding-left: 20px;
  margin-bottom: 0;
}

.info-list li {
  margin-bottom: 10px;
}

/* Form */
.form-group { margin-bottom: 20px; text-align: left; }
label { display: block; margin-bottom: 8px; font-weight: 600; }
input, textarea {
  width: 100%; padding: 12px; border: 1px solid var(--border-color);
  border-radius: 8px; background-color: var(--input-bg);
  color: var(--text-color); font-size: 1rem; box-sizing: border-box;
}

.submit-btn {
  width: 100%; padding: 15px; background-color: var(--button-bg);
  color: white; border: none; border-radius: 8px; font-weight: 700;
  font-size: 1.1rem; cursor: pointer;
}

/* Ad container */
.ad-container { margin-bottom: 30px; text-align: center; overflow: hidden; }

/* Result Bar */
.result-bar-wrapper { display: flex; align-items: center; gap: 15px; margin-bottom: 10px; }
.result-label { width: 80px; font-weight: 700; }
.bar-container { flex-grow: 1; height: 24px; background-color: #e9ecef; border-radius: 12px; overflow: hidden; }
.bar-fill { height: 100%; background-color: var(--button-bg); transition: width 0.5s ease-out; }
.result-percent { width: 50px; font-weight: 700; text-align: right; }

/* Footer */
.footer {
  background-color: var(--footer-bg);
  border-top: 1px solid var(--border-color);
  padding: 40px 0;
  margin-top: 60px;
  text-align: center;
}

.footer-container { max-width: 1000px; margin: 0 auto; padding: 0 20px; }
.footer-links {
  list-style: none; padding: 0; display: flex; justify-content: center; gap: 20px; margin-top: 15px;
}
.footer-links a { text-decoration: none; color: var(--text-color); opacity: 0.7; font-size: 0.9rem; }
.footer-links a:hover { opacity: 1; color: var(--button-bg); }

@media (max-width: 600px) {
  .nav-menu { display: none; } /* Simplified for mobile */
  .hero-section h1 { font-size: 1.8rem; }
}