:root {
  --bg-color: #f8f9fa;
  --text-color: #212529;
  --primary-color: #4A90E2;
  --secondary-color: #6c757d;
  --card-bg: #ffffff;
  --border-color: #dee2e6;
  --nav-bg: #ffffff;
  --footer-bg: #343a40;
  --footer-text: #f8f9fa;
}

[data-theme="dark"] {
  --bg-color: #121212;
  --text-color: #e9ecef;
  --primary-color: #5da5ff;
  --secondary-color: #adb5bd;
  --card-bg: #1e1e1e;
  --border-color: #333333;
  --nav-bg: #1e1e1e;
  --footer-bg: #000000;
  --footer-text: #e9ecef;
}

* {
  box-sizing: border-box;
  scroll-behavior: smooth;
}

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

/* Header & Navigation */
header {
  position: sticky;
  top: 0;
  background-color: var(--nav-bg);
  border-bottom: 1px solid var(--border-color);
  z-index: 1000;
  padding: 0 20px;
}

nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  max-width: 1000px;
  margin: 0 auto;
  height: 70px;
}

.logo {
  font-size: 1.5rem;
  font-weight: bold;
  color: var(--primary-color);
}

.nav-links {
  display: flex;
  list-style: none;
  margin: 0;
  padding: 0;
}

.nav-links li {
  margin-left: 25px;
}

.nav-links a {
  text-decoration: none;
  color: var(--text-color);
  font-weight: 500;
  font-size: 0.95rem;
  transition: color 0.2s;
}

.nav-links a:hover {
  color: var(--primary-color);
}

#theme-toggle {
  background: none;
  border: 1px solid var(--primary-color);
  color: var(--primary-color);
  padding: 6px 12px;
  border-radius: 20px;
  cursor: pointer;
  font-size: 0.85rem;
}

/* Main Content */
main {
  max-width: 800px;
  margin: 0 auto;
  padding: 40px 20px;
}

.hero-section {
  text-align: center;
  padding: 60px 0;
}

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

.hero-section p {
  color: var(--secondary-color);
  font-size: 1.1rem;
}

/* Number Generator */
#number-container {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  margin: 40px 0;
  gap: 15px;
}

#number-container span, .placeholder {
  font-size: 2.2rem;
  font-weight: bold;
  width: 75px;
  height: 90px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  border-radius: 12px;
  background-color: var(--card-bg);
  box-shadow: 0 4px 10px rgba(0,0,0,0.1);
  border: 2px solid var(--border-color);
  transition: transform 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

.group-ball {
  border-color: #E67E22 !important; /* Orange for Group */
  color: #E67E22;
  background: linear-gradient(145deg, var(--card-bg), #fff5e6) !important;
}

[data-theme="dark"] .group-ball {
  background: linear-gradient(145deg, #1e1e1e, #2c1a0a) !important;
}

.digit-ball {
  border-color: var(--primary-color) !important;
}

.placeholder {
  opacity: 0.3;
  filter: grayscale(1);
}

#number-container span:hover {
  transform: scale(1.05) translateY(-5px);
  box-shadow: 0 8px 15px rgba(0,0,0,0.15);
}

.controls {
  margin-top: 20px;
}

#generate-btn {
  background-color: var(--primary-color);
  color: white;
  border: none;
  padding: 15px 40px;
  font-size: 1.2rem;
  font-weight: bold;
  border-radius: 30px;
  cursor: pointer;
  box-shadow: 0 4px 15px rgba(74, 144, 226, 0.3);
  transition: background-color 0.2s, transform 0.1s;
}

#generate-btn:hover {
  filter: brightness(1.1);
  transform: translateY(-2px);
}

#generate-btn:active {
  transform: translateY(0);
}

/* Ad Container */
.ad-container {
  margin: 40px 0;
  padding: 20px;
  background-color: var(--card-bg);
  border-radius: 10px;
  border: 1px dashed var(--border-color);
  min-height: 100px;
}

/* Content Sections */
.content-section {
  margin-top: 80px;
  padding: 40px;
  background-color: var(--card-bg);
  border-radius: 15px;
  box-shadow: 0 2px 10px rgba(0,0,0,0.05);
}

.content-section h2 {
  border-left: 5px solid var(--primary-color);
  padding-left: 15px;
  margin-bottom: 25px;
}

.content-section h3 {
  margin-top: 30px;
}

/* Comments */
#comments {
  margin-top: 80px;
}

/* Contact Form */
#contact-form {
  margin-top: 80px;
  padding: 40px;
  background-color: var(--card-bg);
  border-radius: 15px;
}

.form-group {
  margin-bottom: 20px;
  display: flex;
  flex-direction: column;
}

.form-group label {
  margin-bottom: 8px;
  font-weight: 600;
}

.form-group input, .form-group textarea {
  padding: 12px;
  border: 1px solid var(--border-color);
  border-radius: 8px;
  background-color: var(--bg-color);
  color: var(--text-color);
}

#submit-btn {
  width: 100%;
  padding: 15px;
  background-color: var(--primary-color);
  color: white;
  border: none;
  border-radius: 8px;
  font-weight: bold;
  cursor: pointer;
}

/* Footer */
footer {
  margin-top: 100px;
  background-color: var(--footer-bg);
  color: var(--footer-text);
  padding: 60px 20px;
}

.footer-content {
  max-width: 1000px;
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
}

.footer-links {
  list-style: none;
  display: flex;
  padding: 0;
}

.footer-links li {
  margin-left: 20px;
}

.footer-links a {
  color: var(--footer-text);
  text-decoration: none;
  font-size: 0.9rem;
  opacity: 0.8;
}

.footer-links a:hover {
  opacity: 1;
}

/* Responsive */
@media (max-width: 768px) {
  nav {
    flex-direction: column;
    height: auto;
    padding: 20px 0;
  }
  .nav-links {
    margin: 15px 0;
  }
  .nav-links li {
    margin: 0 10px;
  }
  .footer-content {
    flex-direction: column;
    text-align: center;
  }
  .footer-links {
    margin-top: 20px;
  }
  .footer-links li {
    margin: 0 10px;
  }
}