/* ========================================
   AI 아바타 영상 강의 - 모던 디자인 (2025)
======================================== */

/* ========== 기본 설정 및 변수 ========== */
:root {
  --primary-color: #6366f1;
  --primary-dark: #4f46e5;
  --primary-light: #a5b4fc;
  --secondary-color: #f59e0b;
  --accent-color: #10b981;
  --text-primary: #1f2937;
  --text-secondary: #6b7280;
  --text-light: #9ca3af;
  --bg-primary: #ffffff;
  --bg-secondary: #f9fafb;
  --bg-accent: #f3f4f6;
  --border-color: #e5e7eb;
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
  --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
}

/* ========== 기본 스타일 ========== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Noto Sans KR', sans-serif;
  line-height: 1.6;
  color: var(--text-primary);
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  min-height: 100vh;
  padding: 2rem 1rem;
}

.container {
  max-width: 900px;
  margin: 0 auto;
  background: var(--bg-primary);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-xl);
  overflow: hidden;
  position: relative;
}

/* ========== 헤더 ========== */
header {
  background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-dark) 100%);
  color: white;
  padding: 4rem 3rem;
  text-align: center;
  position: relative;
  overflow: hidden;
}

header::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: url('data:image/svg+xml,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100"><defs><pattern id="grain" width="100" height="100" patternUnits="userSpaceOnUse"><circle cx="25" cy="25" r="1" fill="white" opacity="0.1"/><circle cx="75" cy="75" r="1" fill="white" opacity="0.1"/><circle cx="50" cy="10" r="0.5" fill="white" opacity="0.1"/><circle cx="10" cy="60" r="0.5" fill="white" opacity="0.1"/><circle cx="90" cy="40" r="0.5" fill="white" opacity="0.1"/></pattern></defs><rect width="100" height="100" fill="url(%23grain)"/></svg>');
  pointer-events: none;
}

header h1 {
  font-size: 3rem;
  font-weight: 600;
  margin-bottom: 1rem;
  position: relative;
  z-index: 1;
  background: linear-gradient(45deg, #ffffff, #e0e7ff);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

header p {
  font-size: 1.25rem;
  opacity: 0.9;
  position: relative;
  z-index: 1;
  font-weight: 300;
}

/* ========== 섹션 공통 스타일 ========== */
section {
  padding: 3rem;
  border-bottom: 1px solid var(--border-color);
}

section:last-child {
  border-bottom: none;
}

section h2 {
  font-size: 2rem;
  font-weight: 500;
  color: var(--text-primary);
  margin-bottom: 1.5rem;
  position: relative;
  display: inline-block;
}

section h2::after {
  content: '';
  position: absolute;
  bottom: -0.5rem;
  left: 0;
  width: 3rem;
  height: 0.25rem;
  background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
  border-radius: var(--radius-sm);
}

section p {
  color: var(--text-secondary);
  font-size: 1.1rem;
  line-height: 1.7;
  margin-bottom: 1.5rem;
}

/* ========== 버튼 스타일 ========== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.875rem 2rem;
  background: linear-gradient(135deg, var(--primary-color), var(--primary-dark));
  color: white;
  text-decoration: none;
  border-radius: var(--radius-lg);
  font-weight: 500;
  font-size: 1rem;
  border: none;
  cursor: pointer;
  transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  box-shadow: var(--shadow-md);
  position: relative;
  overflow: hidden;
}

.btn::before {
  content: '';
  position: absolute;
  top: 0;
  left: -100%;
  width: 100%;
  height: 100%;
  background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
  transition: left 0.5s;
}

.btn:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.btn:hover::before {
  left: 100%;
}

.btn:active {
  transform: translateY(0);
}

.btn-secondary {
  background: linear-gradient(135deg, var(--secondary-color), #f59e0b);
}

.btn-success {
  background: linear-gradient(135deg, var(--accent-color), #059669);
}

/* ========== 특별 섹션 스타일 ========== */
.youtube-intro {
  background: linear-gradient(135deg, #f8fafc, #e2e8f0);
  padding: 2.5rem;
  border-radius: var(--radius-lg);
  text-align: center;
  margin-top: 2rem;
  border: 1px solid var(--border-color);
  position: relative;
}

.youtube-intro::before {
  content: '🎥';
  position: absolute;
  top: -1rem;
  left: 50%;
  transform: translateX(-50%);
  background: var(--bg-primary);
  padding: 0.5rem;
  border-radius: 50%;
  font-size: 1.5rem;
  box-shadow: var(--shadow-md);
}

.youtube-intro p {
  margin-bottom: 1.5rem;
  font-weight: 500;
}

.centered-section {
  text-align: center;
  background: var(--bg-secondary);
  margin: 0 -3rem;
  padding: 4rem 3rem;
}

/* ========== 링크 버튼 그리드 ========== */
#links .buttons {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1rem;
  margin-top: 2rem;
}

#links .btn {
  width: 100%;
  padding: 1rem;
  font-size: 0.95rem;
}

/* 각 링크별 색상 */
.btn-freepik { background: linear-gradient(135deg, #ff6b6b, #ee5a52); }
.btn-kling { background: linear-gradient(135deg, #4ecdc4, #44a08d); }
.btn-whisk { background: linear-gradient(135deg, #a8edea, #fed6e3); color: var(--text-primary); }
.btn-deepl { background: linear-gradient(135deg, #0f4c75, #3282b8); }
.btn-gemini { background: linear-gradient(135deg, #667eea, #764ba2); }
.btn-gpt { background: linear-gradient(135deg, #74b9ff, #0984e3); }
.btn-slides { background: linear-gradient(135deg, #fdcb6e, #e17055); }

/* ========== 폼 스타일 ========== */
.form-group {
  margin-bottom: 1.5rem;
  text-align: left;
}

.form-group label {
  display: block;
  margin-bottom: 0.5rem;
  font-weight: 500;
  color: var(--text-primary);
  font-size: 0.95rem;
}

#review-form input[type="text"],
#review-form textarea {
  width: 100%;
  padding: 1rem;
  border: 2px solid var(--border-color);
  border-radius: var(--radius-md);
  font-size: 1rem;
  font-family: inherit;
  transition: all 0.3s ease;
  background: var(--bg-primary);
}

#review-form input[type="text"]:focus,
#review-form textarea:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
  transform: translateY(-1px);
}

#review-form textarea {
  resize: vertical;
  min-height: 120px;
  line-height: 1.6;
}

/* ========== 후기 목록 ========== */
.review-list {
  margin-top: 2rem;
  text-align: left;
}

.review-item {
  background: var(--bg-secondary);
  padding: 1.5rem;
  border-radius: var(--radius-md);
  margin-bottom: 1rem;
  border-left: 4px solid var(--primary-color);
  box-shadow: var(--shadow-sm);
}

.review-item .author {
  font-weight: 500;
  color: var(--primary-color);
  margin-bottom: 0.5rem;
}

.review-item .content {
  color: var(--text-secondary);
  line-height: 1.6;
}

.thanks-msg {
  text-align: center;
  margin-top: 2rem;
  color: var(--text-light);
  font-style: italic;
  font-size: 0.95rem;
}

/* ========== 반응형 디자인 ========== */
@media (max-width: 768px) {
  body {
    padding: 1rem 0.5rem;
  }
  
  .container {
    margin: 0;
    border-radius: 0;
  }
  
  header {
    padding: 3rem 2rem;
  }
  
  header h1 {
    font-size: 2.5rem;
  }
  
  section {
    padding: 2rem 1.5rem;
  }
  
  .centered-section {
    margin: 0 -1.5rem;
    padding: 3rem 1.5rem;
  }
  
  #links .buttons {
    grid-template-columns: 1fr;
  }
  
  .btn {
    padding: 1rem 1.5rem;
  }
}

@media (max-width: 480px) {
  header h1 {
    font-size: 2rem;
  }
  
  header p {
    font-size: 1.1rem;
  }
  
  section h2 {
    font-size: 1.75rem;
  }
  
  section {
    padding: 1.5rem 1rem;
  }
  
  .centered-section {
    margin: 0 -1rem;
    padding: 2.5rem 1rem;
  }
}

/* ========== 애니메이션 ========== */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

section {
  animation: fadeInUp 0.6s ease-out;
}

/* ========== 스크롤바 스타일 ========== */
::-webkit-scrollbar {
  width: 8px;
}

::-webkit-scrollbar-track {
  background: var(--bg-secondary);
}

::-webkit-scrollbar-thumb {
  background: var(--primary-light);
  border-radius: var(--radius-sm);
}

::-webkit-scrollbar-thumb:hover {
  background: var(--primary-color);
}