:root {
  /* 눈이 편안한 파스텔톤/뮤트톤 색상 */
  --primary-color: #5c7cfa;
  --primary-hover: #4c6ef5;
  --primary-gradient: linear-gradient(135deg, #748ffc 0%, #5c7cfa 100%);
  
  --secondary-color: #f1f3f5;
  --success-color: #51cf66;
  --success-gradient: linear-gradient(135deg, #69db7c 0%, #51cf66 100%);
  --danger-color: #ff8787;
  --danger-gradient: linear-gradient(135deg, #ffa8a8 0%, #ff8787 100%);
  --voca-quiz-gradient: linear-gradient(135deg, #b197fc 0%, #9775fa 100%);
  
  --text-primary: #343a40;
  --text-muted: #868e96;
  --text-light: #ffffff;
  --bg-color: #f8f9fa;
  --card-bg: #ffffff;
  --border-color: #dee2e6;
  --card-shadow: 0 10px 25px rgba(0, 0, 0, 0.05);
  --btn-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
  --transition: all 0.25s ease;
}

body.dark-mode {
  --text-primary: #f8f9fa;
  --text-muted: #adb5bd;
  --bg-color: #1a1b1e;
  --card-bg: #25262b;
  --border-color: #373a40;
  --secondary-color: #2c2e33;
}

* { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: 'Pretendard', -apple-system, sans-serif;
  background-color: var(--bg-color);
  color: var(--text-primary);
  line-height: 1.6;
  transition: var(--transition);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* Header & Nav */
header {
  background: var(--card-bg);
  border-bottom: 1px solid var(--border-color);
  position: sticky;
  top: 0;
  z-index: 100;
}

.nav-container {
  max-width: 1000px;
  margin: 0 auto;
  padding: 0 20px;
  height: 65px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo { font-size: 20px; font-weight: 800; color: var(--primary-color); cursor: pointer; }

.nav-menu { display: flex; list-style: none; gap: 8px; }
.nav-menu li {
  padding: 8px 16px;
  border-radius: 10px;
  font-size: 14px;
  font-weight: 700;
  cursor: pointer;
  color: var(--text-muted);
  transition: var(--transition);
  background: var(--secondary-color);
  border: 1px solid var(--border-color);
}
.nav-menu li:hover {
  background: var(--card-bg);
  color: var(--primary-color);
  border-color: var(--primary-color);
  transform: translateY(-2px);
}

#theme-btn {
  background: var(--secondary-color);
  border: 1px solid var(--border-color);
  width: 40px; height: 40px;
  border-radius: 10px;
  cursor: pointer;
  font-size: 18px;
  transition: var(--transition);
}
#theme-btn:hover { transform: scale(1.05); background: var(--card-bg); border-color: var(--primary-color); }

/* Main Container */
.container { flex: 1; width: 100%; max-width: 700px; margin: 30px auto; padding: 0 20px; }
section { background: var(--card-bg); padding: 35px; border-radius: 24px; box-shadow: var(--card-shadow); text-align: center; }

h1 { font-size: 30px; font-weight: 800; margin-bottom: 8px; }
.site-intro { color: var(--text-muted); margin-bottom: 30px; font-size: 16px; }

/* Global Button Component */
.btn-main, #next-btn, .ex-speak-btn, #speak-btn, .btn-add-voca {
  padding: 14px 24px;
  border-radius: 12px;
  border: 1px solid transparent;
  font-weight: 700;
  font-size: 15px;
  cursor: pointer;
  transition: var(--transition);
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  box-shadow: var(--btn-shadow);
  color: white; /* 기본 버튼 글자색을 흰색으로 설정 */
}

.btn-main:hover, #next-btn:hover, .btn-add-voca:hover { transform: translateY(-2px); filter: brightness(1.05); }
.btn-main:active, #next-btn:active, .btn-add-voca:active { transform: translateY(0); filter: brightness(1); } /* 클릭 시 색 변화 방지 */

/* Primary Action Buttons */
.btn-start { background: var(--primary-gradient); color: white; width: 100%; margin-bottom: 12px; font-size: 17px; }
.action-btns { display: flex; gap: 12px; }
.btn-review { background: #adb5bd; color: white; flex: 1; }
.btn-voca-quiz { background: var(--voca-quiz-gradient); color: white; flex: 1; }

.btn-save, .btn-add-voca { background: var(--primary-gradient); color: white; padding: 10px 20px; font-size: 14px; }

/* Next Button - Fixed Style */
#next-btn {
  background: var(--success-gradient);
  color: white;
  width: 100%;
  margin: 20px 0;
  font-size: 17px;
  font-weight: 800;
  display: none;
  box-shadow: 0 8px 20px rgba(81, 207, 102, 0.25);
}

/* Speak Buttons */
#speak-btn, .ex-speak-btn {
  background: white;
  color: var(--primary-color);
  border: 1px solid var(--primary-color);
  padding: 8px 16px;
  font-size: 13px;
  box-shadow: var(--btn-shadow);
  margin: 0 auto 15px;
}
#speak-btn:hover, .ex-speak-btn:hover { background: var(--primary-color); color: white; }

/* Choice Buttons */
.choices-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin: 25px 0; }
.choice {
  padding: 18px;
  font-size: 16px;
  border-radius: 14px;
  background: var(--secondary-color);
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
}
.choice:hover { border-color: var(--primary-color); background: var(--card-bg); box-shadow: var(--btn-shadow); transform: translateY(-2px); }
.choice.correct { background: var(--success-gradient) !important; color: white !important; border-color: transparent !important; }
.choice.wrong { background: var(--danger-gradient) !important; color: white !important; border-color: transparent !important; }

/* Mode Switcher - 텍스트 링크 방지용 대대적 수정 */
.btn-group {
  display: flex;
  gap: 10px;
  background: var(--secondary-color);
  padding: 8px;
  border-radius: 16px;
  border: 2px solid var(--border-color);
  margin: 10px 0;
}
.btn-group button {
  flex: 1;
  padding: 12px;
  border: 1px solid var(--border-color);
  border-radius: 10px;
  font-weight: 800;
  font-size: 14px;
  cursor: pointer;
  transition: var(--transition);
  background: var(--card-bg); /* 기본 배경을 흰색으로 고정 */
  color: var(--text-muted);
  box-shadow: 0 2px 5px rgba(0,0,0,0.05);
}
.btn-group button.active {
  background: var(--primary-gradient) !important;
  color: white !important;
  border-color: transparent !important;
  box-shadow: 0 5px 15px rgba(92, 124, 250, 0.35);
}
.btn-group button:hover:not(.active) {
  background: var(--bg-color);
  color: var(--primary-color);
  border-color: var(--primary-color);
}

/* Limit Select */
#limit-select {
  width: 100%; padding: 12px; border-radius: 12px; border: 1px solid var(--border-color); background: var(--secondary-color); color: var(--text-primary); font-weight: 700; outline: none; cursor: pointer;
}

/* Layout Elements */
#word { font-size: 48px; font-weight: 800; margin-bottom: 15px; color: var(--primary-color); }
#example-box {
  margin-top: 25px;
  padding: 20px;
  background: var(--secondary-color);
  border-radius: 16px;
  text-align: left;
  border-left: 4px solid var(--primary-color);
}

/* Content Pages */
.content-page { text-align: left; line-height: 1.8; }
.section-title { font-size: 28px; font-weight: 800; margin-bottom: 25px; color: var(--text-primary); border-bottom: 3px solid var(--primary-color); display: inline-block; padding-bottom: 5px; }

.prose h3 { font-size: 20px; font-weight: 700; margin: 30px 0 15px; color: var(--primary-color); }
.prose p { margin-bottom: 18px; color: var(--text-primary); font-size: 16px; }

/* Article Card Styles */
.article-card {
  background: var(--bg-color);
  padding: 25px;
  border-radius: 16px;
  margin-bottom: 25px;
  border: 1px solid var(--border-color);
  transition: var(--transition);
}
.article-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--card-shadow);
  border-color: var(--primary-color);
}
.article-card h3 {
  margin-top: 0;
}

/* Tabs for About Section */
.tab-container { margin-top: 20px; }
.tab-menu { display: flex; flex-wrap: wrap; gap: 8px; border-bottom: 2px solid var(--border-color); padding-bottom: 10px; margin-bottom: 25px; }
.tab-btn {
  padding: 10px 18px;
  border-radius: 12px;
  border: 1px solid var(--border-color);
  background: var(--secondary-color);
  color: var(--text-muted);
  font-weight: 700;
  font-size: 14px;
  cursor: pointer;
  transition: var(--transition);
}
.tab-btn:hover { background: var(--bg-color); color: var(--primary-color); border-color: var(--primary-color); }
.tab-btn.active { background: var(--primary-gradient); color: white; border-color: transparent; box-shadow: var(--btn-shadow); }

.tab-content { display: none; animation: fadeIn 0.4s ease; }
.tab-content.active { display: block; }
.tab-content h3 { font-size: 20px; font-weight: 700; margin-bottom: 15px; color: var(--primary-color); }
.tab-content p, .tab-content li { font-size: 15px; color: var(--text-primary); margin-bottom: 12px; }
.tab-content ul { padding-left: 20px; margin-bottom: 20px; }
.tab-content a { color: var(--primary-color); text-decoration: none; font-weight: 700; }
.tab-content a:hover { text-decoration: underline; }

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Ad Container */
.ad-container { margin-top: 40px; padding: 20px; background: var(--secondary-color); border-radius: 16px; min-height: 100px; display: flex; align-items: center; justify-content: center; border: 1px dashed var(--border-color); }

/* Word of the Day Card */
#wotd-container { margin-bottom: 30px; }
.wotd-card {
  background: var(--card-bg);
  border: 2px solid var(--primary-color);
  border-radius: 20px;
  padding: 25px;
  text-align: left;
  position: relative;
  overflow: hidden;
  box-shadow: var(--card-shadow);
}
.wotd-tag {
  display: inline-block;
  background: var(--primary-color);
  color: white;
  padding: 4px 12px;
  border-radius: 8px;
  font-size: 12px;
  font-weight: 800;
  margin-bottom: 12px;
}
.wotd-word { font-size: 32px; font-weight: 800; color: var(--primary-color); margin-bottom: 5px; }
.wotd-meaning { font-size: 18px; font-weight: 700; color: var(--text-primary); margin-bottom: 10px; }
.wotd-ex { font-size: 14px; color: var(--text-muted); font-style: italic; border-top: 1px solid var(--border-color); padding-top: 10px; }

/* Voca List Styles */
#voca-list { list-style: none; margin-top: 15px; overflow-y: auto; flex: 1; padding-right: 5px; }
#voca-list li { display: flex; justify-content: space-between; align-items: center; padding: 8px 12px; background: var(--secondary-color); border-radius: 10px; margin-bottom: 6px; border: 1px solid var(--border-color); }
.voca-item-info { display: flex; flex-direction: row; align-items: center; gap: 8px; flex: 1; overflow: hidden; }
.voca-word-text { font-weight: 800; color: var(--primary-color); font-size: 14px; }
.voca-meaning-text { font-size: 12px; color: var(--text-muted); font-weight: 600; }
.delete-voca-btn { background: var(--card-bg); border: 1px solid var(--border-color); color: var(--danger-color); font-size: 16px; width: 24px; height: 24px; border-radius: 6px; cursor: pointer; display: flex; align-items: center; justify-content: center; opacity: 0.7; }
.delete-voca-btn:hover { opacity: 1; background: var(--danger-color); color: white; border-color: transparent; }

/* Floating Voca Container */
#my-voca-container { position: fixed; bottom: 25px; right: 25px; z-index: 999; }
#voca-toggle-btn { padding: 14px 24px; border-radius: 50px; background: var(--primary-gradient); color: white; border: none; font-weight: 700; box-shadow: 0 8px 20px rgba(92, 124, 250, 0.3); cursor: pointer; transition: var(--transition); }
#voca-toggle-btn:hover { transform: translateY(-3px); box-shadow: 0 12px 25px rgba(92, 124, 250, 0.4); }

#voca-content { position: absolute; bottom: 70px; right: 0; width: 300px; max-height: 450px; background: var(--card-bg); border-radius: 20px; box-shadow: 0 15px 35px rgba(0,0,0,0.15); border: 1px solid var(--border-color); padding: 20px; display: flex; flex-direction: column; }

/* Footer */
footer { padding: 50px 20px; text-align: center; color: var(--text-muted); }
.footer-links { margin-top: 20px; display: flex; justify-content: center; gap: 10px; }
.footer-links span {
  padding: 8px 16px;
  border-radius: 10px;
  font-size: 13px;
  font-weight: 700;
  cursor: pointer;
  transition: var(--transition);
  background: var(--secondary-color);
  border: 1px solid var(--border-color);
}
.footer-links span:hover { background: var(--card-bg); color: var(--primary-color); border-color: var(--primary-color); transform: translateY(-2px); }

@media (max-width: 600px) {
  .nav-menu { display: none; }
  .choices-grid { grid-template-columns: 1fr; }
  .action-btns { flex-direction: column; gap: 10px; }
}