:root {
  --yellow: #FFD93D;
  --coral: #FF6B6B;
  --mint: #6BCB77;
  --blue: #4D96FF;
  --purple: #C77DFF;
  --orange: #FF9A3C;
  --bg: #fef9f0;
  --card: #ffffff;
  --text: #2d2d2d;
  --sub: #888;
  --border: #e0d6c8;
}

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

body {
  font-family: 'Noto Sans KR', sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
}

/* 광고 영역 */
.ad-slot {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 90px;
  margin: 16px auto;
  max-width: 820px;
  border: 1px dashed #d8cdb9;
  border-radius: 12px;
  background: #fffdf8;
}

.ad-label {
  font-size: 12px;
  letter-spacing: 0.05em;
  color: #bbb;
}

/* HEADER */
.tools_header {
  background: linear-gradient(135deg, #6BCB77 0%, #4D96FF 100%);
  padding: 36px 20px 28px;
  text-align: center;
  position: relative;
  overflow: hidden;
}
.tools_header::before {
  content: '';
  position: absolute;
  top: -40px; right: -40px;
  width: 180px; height: 180px;
  background: rgba(255,255,255,0.15);
  border-radius: 50%;
}
.tools_header::after {
  content: '';
  position: absolute;
  bottom: -60px; left: -30px;
  width: 220px; height: 220px;
  background: rgba(255,255,255,0.10);
  border-radius: 50%;
}
.tools_header h1 {
  font-family: 'Gaegu', cursive;
  font-size: 2.6rem;
  color: #fff;
  text-shadow: 2px 3px 0 rgba(0,0,0,0.12);
  position: relative; z-index: 1;
}
.tools_header p {
  color: rgba(255,255,255,0.92);
  font-size: 0.95rem;
  margin-top: 6px;
  position: relative; z-index: 1;
}

/* MAIN */
.tools_main {
  max-width: 820px;
  margin: 0 auto;
  padding: 28px 16px 0;
}

/* INPUT SECTION */
.input-section {
  background: var(--card);
  border-radius: 24px;
  padding: 28px 24px;
  box-shadow: 0 4px 24px rgba(0,0,0,0.07);
  border: 2px solid var(--border);
}

.input-section h2 {
  font-family: 'Gaegu', cursive;
  font-size: 1.4rem;
  margin-bottom: 20px;
  color: #444;
}

.num-input-row {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 16px;
  flex-wrap: wrap;
}

.num-box {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 6px;
}

.num-box label {
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--sub);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.num-box input {
  width: 90px;
  height: 72px;
  border: 2.5px solid var(--border);
  border-radius: 18px;
  text-align: center;
  font-family: 'Gaegu', cursive;
  font-size: 2.4rem;
  font-weight: 700;
  color: var(--text);
  background: #fafafa;
  outline: none;
  transition: border-color 0.2s, box-shadow 0.2s;
  -moz-appearance: textfield;
}
.num-box input::-webkit-inner-spin-button { display: none; }
.num-box input:focus {
  border-color: var(--mint);
  box-shadow: 0 0 0 3px rgba(107,203,119,0.25);
  background: #fff;
}

.op-sign {
  font-family: 'Gaegu', cursive;
  font-size: 2.6rem;
  color: #aaa;
  margin-top: 20px;
}

.eq-sign {
  font-family: 'Gaegu', cursive;
  font-size: 2.4rem;
  color: #aaa;
  margin-top: 20px;
}

.result-badge {
  background: linear-gradient(135deg, #6BCB77, #4D96FF);
  color: white;
  border-radius: 18px;
  width: 90px;
  height: 72px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: 'Gaegu', cursive;
  font-size: 2.4rem;
  font-weight: 700;
  margin-top: 20px;
  box-shadow: 0 4px 14px rgba(77,150,255,0.3);
  transition: all 0.3s;
}

.actions {
  display: flex;
  gap: 10px;
  margin-top: 22px;
}

.btn-visualize {
  flex: 1;
  background: linear-gradient(135deg, #6BCB77, #4D96FF);
  color: #fff;
  border: none;
  border-radius: 14px;
  padding: 14px 20px;
  font-family: 'Gaegu', cursive;
  font-size: 1.3rem;
  cursor: pointer;
  box-shadow: 0 4px 14px rgba(77,150,255,0.3);
  transition: transform 0.15s, box-shadow 0.15s;
}
.btn-visualize:hover { transform: translateY(-2px); box-shadow: 0 6px 20px rgba(77,150,255,0.4); }
.btn-visualize:active { transform: translateY(0); }

.btn-reset {
  background: #f0f0f0; border: 2px solid #e0e0e0;
  color: #888; border-radius: 14px; padding: 14px 18px;
  font-size: 0.9rem; cursor: pointer; transition: all 0.2s;
  font-family: 'Noto Sans KR', sans-serif;
}
.btn-reset:hover { background: #e8e8e8; }

.quick-examples {
  margin-top: 14px;
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  align-items: center;
}
.quick-examples span {
  font-size: 0.8rem; color: var(--sub); white-space: nowrap;
}
.chip {
  background: #f4f4f4; border: 1px solid #e0e0e0;
  border-radius: 20px; padding: 5px 12px;
  font-family: 'Gaegu', cursive; font-size: 0.95rem;
  cursor: pointer; transition: all 0.15s; color: #555;
}
.chip:hover { background: var(--mint); border-color: var(--mint); color: #fff; }

.error-msg {
  color: var(--coral);
  font-size: 0.85rem;
  margin-top: 10px;
  display: none;
}

#result {
  margin-top: 28px;
  display: none;
}

.result-title {
  font-family: 'Gaegu', cursive;
  font-size: 1.6rem;
  margin-bottom: 18px;
  color: #444;
  text-align: center;
}

.array-section {
  background: var(--card);
  border-radius: 24px;
  padding: 28px 24px;
  box-shadow: 0 4px 24px rgba(0,0,0,0.07);
  border: 2px solid var(--border);
  margin-bottom: 20px;
}

.array-section h3 {
  font-family: 'Gaegu', cursive;
  font-size: 1.25rem;
  color: #444;
  margin-bottom: 18px;
  text-align: center;
}

.mode-tabs {
  display: flex;
  gap: 8px;
  margin-bottom: 20px;
  justify-content: center;
  flex-wrap: wrap;
}

.mode-tab {
  padding: 8px 18px;
  border-radius: 20px;
  border: 2px solid var(--border);
  background: #f5f5f5;
  font-family: 'Gaegu', cursive;
  font-size: 1rem;
  cursor: pointer;
  transition: all 0.2s;
  color: #888;
}
.mode-tab.active {
  background: linear-gradient(135deg, #6BCB77, #4D96FF);
  border-color: transparent;
  color: white;
  box-shadow: 0 3px 12px rgba(77,150,255,0.3);
}

.dot-array-wrap {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  overflow-x: auto;
  padding: 12px 4px;
}

.dot-row {
  display: flex;
  gap: 8px;
  align-items: center;
}

.dot {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  opacity: 0;
  transform: scale(0);
  animation: multDotPop 0.3s cubic-bezier(0.34, 1.56, 0.64, 1) forwards;
}

@keyframes multDotPop {
  to { opacity: 1; transform: scale(1); }
}

.row-label {
  font-family: 'Gaegu', cursive;
  font-size: 0.9rem;
  color: #aaa;
  min-width: 30px;
  text-align: right;
}

.col-labels {
  display: flex;
  gap: 8px;
  margin-bottom: 2px;
}
.col-label {
  width: 36px;
  text-align: center;
  font-family: 'Gaegu', cursive;
  font-size: 0.85rem;
  color: #bbb;
}

/* 묶음으로 보기: 행마다 점선 테두리로 그룹을 감싼다 */
.dot-group {
  display: flex;
  align-items: center;
  gap: 10px;
  border: 2px dashed #ddd;
  border-radius: 12px;
  padding: 4px 10px;
}
.group-tag {
  font-family: 'Gaegu', cursive;
  font-size: 0.85rem;
  color: #aaa;
  white-space: nowrap;
}

.array-legend {
  margin-top: 16px;
  display: flex;
  gap: 16px;
  justify-content: center;
  flex-wrap: wrap;
}

.legend-item {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.85rem;
  color: #555;
}

.legend-dot {
  width: 24px; height: 24px;
  border-radius: 50%;
}

.commutative-section {
  background: var(--card);
  border-radius: 24px;
  padding: 24px 22px;
  box-shadow: 0 4px 18px rgba(0,0,0,0.07);
  border: 2px solid var(--border);
  margin-bottom: 20px;
  animation: multFadeUp 0.5s ease both 0.1s;
}

@keyframes multFadeUp {
  from { opacity: 0; transform: translateY(16px); }
  to   { opacity: 1; transform: translateY(0); }
}

.commutative-section h3 {
  font-family: 'Gaegu', cursive;
  font-size: 1.25rem;
  color: #444;
  margin-bottom: 16px;
  text-align: center;
}

.comm-visual {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 24px;
  flex-wrap: wrap;
}

.comm-box {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 10px;
}

.comm-label {
  font-family: 'Gaegu', cursive;
  font-size: 1.5rem;
  font-weight: 700;
}

.mini-array {
  display: flex;
  flex-direction: column;
  gap: 4px;
  border-radius: 12px;
  padding: 8px;
  border: 2px solid var(--border);
  background: #fafafa;
}

.mini-row {
  display: flex;
  gap: 4px;
}

.mini-dot {
  width: 20px; height: 20px;
  border-radius: 50%;
}

.swap-arrow {
  font-size: 2rem;
  color: #ccc;
  animation: multPulse 1.5s ease-in-out infinite;
}
@keyframes multPulse {
  0%, 100% { transform: scale(1); opacity: 0.6; }
  50% { transform: scale(1.15); opacity: 1; }
}

.comm-explain {
  margin-top: 16px;
  background: #f0fff4;
  border: 2px dashed #6BCB77;
  border-radius: 14px;
  padding: 12px 16px;
  font-size: 0.88rem;
  color: #333;
  line-height: 1.7;
  text-align: center;
}
.comm-explain strong { color: #2d9e40; }

.multiples-section {
  background: var(--card);
  border-radius: 24px;
  padding: 24px 22px;
  box-shadow: 0 4px 18px rgba(0,0,0,0.07);
  border: 2px solid var(--border);
  margin-bottom: 20px;
  animation: multFadeUp 0.5s ease both 0.2s;
}

.multiples-section h3 {
  font-family: 'Gaegu', cursive;
  font-size: 1.25rem;
  color: #444;
  margin-bottom: 16px;
  text-align: center;
}

.multiples-track {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  justify-content: center;
}

.mult-chip {
  padding: 8px 14px;
  border-radius: 12px;
  font-family: 'Gaegu', cursive;
  font-size: 1.1rem;
  font-weight: 700;
  border: 2px solid transparent;
  transition: all 0.25s;
  opacity: 0;
  animation: multChipFade 0.3s ease forwards;
  position: relative;
}
@keyframes multChipFade {
  to { opacity: 1; }
}

.mult-chip.highlight {
  box-shadow: 0 4px 12px rgba(0,0,0,0.15);
  transform: scale(1.08);
}

.mult-chip .step-label {
  position: absolute;
  top: -18px;
  left: 50%;
  transform: translateX(-50%);
  font-size: 0.72rem;
  font-family: 'Noto Sans KR', sans-serif;
  color: #aaa;
  white-space: nowrap;
}

.tip-box {
  margin-top: 16px;
  background: white;
  border-radius: 12px;
  padding: 12px 16px;
  font-size: 0.88rem;
  color: #555;
  line-height: 1.7;
  border-left: 4px solid var(--yellow);
  text-align: left;
}
.tip-box strong { color: #333; }

.summary-card {
  background: linear-gradient(135deg, #e8f8ec, #e8f0ff);
  border-radius: 20px;
  padding: 22px;
  border: 2px solid #c5e8cf;
  text-align: center;
  margin-bottom: 20px;
  animation: multFadeUp 0.5s ease both 0.15s;
}

.summary-eq {
  font-family: 'Gaegu', cursive;
  font-size: 2.4rem;
  font-weight: 700;
  color: #2a6db5;
  margin-bottom: 8px;
}

.summary-eq .num-a { color: #FF6B6B; }
.summary-eq .num-b { color: #4D96FF; }
.summary-eq .num-c { color: #2d9e40; }

.summary-desc {
  font-size: 0.9rem;
  color: #555;
  line-height: 1.8;
}

.tools_footer {
  text-align: center;
  padding: 40px 20px 20px;
  font-size: 0.8rem;
  color: #bbb;
}

@media (max-width: 520px) {
  .tools_header h1 { font-size: 2rem; }
  .dot { width: 28px; height: 28px; }
  .dot-row { gap: 5px; }
  .col-label { width: 28px; }
  .col-labels { gap: 5px; }
  .mini-dot { width: 15px; height: 15px; }
  .mini-row { gap: 3px; }
  .mini-array { gap: 3px; padding: 6px; }
}