:root {
  --bg: #0f1115;
  --panel: #171a21;
  --panel-2: #1e222b;
  --border: #2a2f3a;
  --text: #e6e9ef;
  --muted: #8b93a3;
  --accent: #6c8cff;
  --accent-2: #4f6bff;
  --danger: #ff6b6b;
  --checker-a: #2a2f3a;
  --checker-b: #232733;
  --radius: 14px;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: "Pretendard", -apple-system, BlinkMacSystemFont, "Segoe UI",
    Roboto, "Helvetica Neue", Arial, "Apple SD Gothic Neo", "Noto Sans KR",
    sans-serif;
  background: radial-gradient(1200px 600px at 50% -10%, #1a1f2b 0%, var(--bg) 60%);
  color: var(--text);
  min-height: 100vh;
}

.topbar {
  padding: 22px 28px;
  border-bottom: 1px solid var(--border);
  background: rgba(15, 17, 21, 0.6);
  backdrop-filter: blur(8px);
  position: sticky;
  top: 0;
  z-index: 10;
}

.brand { display: flex; align-items: center; gap: 14px; }
.brand .logo { font-size: 30px; }
.brand h1 { margin: 0; font-size: 20px; letter-spacing: -0.3px; }
.brand p { margin: 2px 0 0; font-size: 13px; color: var(--muted); }

main { max-width: 1180px; margin: 0 auto; padding: 28px; }

/* 드롭 존 */
.drop-zone {
  border: 2px dashed var(--border);
  border-radius: 20px;
  background: var(--panel);
  padding: 60px 24px;
  text-align: center;
  cursor: pointer;
  transition: border-color 0.15s, background 0.15s, transform 0.1s;
}
.drop-zone:hover { border-color: var(--accent); background: var(--panel-2); }
.drop-zone.dragover {
  border-color: var(--accent);
  background: #1c2233;
  transform: scale(1.005);
}
.drop-icon { font-size: 52px; }
.drop-title { font-size: 18px; margin: 14px 0 4px; font-weight: 600; }
.drop-sub { color: var(--muted); margin: 0; font-size: 14px; }

/* 워크스페이스 */
.workspace {
  display: grid;
  grid-template-columns: 300px 1fr;
  gap: 24px;
  align-items: start;
}
@media (max-width: 900px) {
  .workspace { grid-template-columns: 1fr; }
}

.controls {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  position: sticky;
  top: 96px;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.control-group { display: flex; flex-direction: column; gap: 8px; }
.control-group label {
  font-size: 14px;
  font-weight: 600;
  display: flex;
  flex-direction: column;
  gap: 2px;
}
.control-group .hint { font-weight: 400; font-size: 12px; color: var(--muted); }
.control-group input[type="range"] { width: 100%; accent-color: var(--accent); }
.control-group output {
  font-variant-numeric: tabular-nums;
  font-size: 13px;
  color: var(--accent);
  align-self: flex-end;
  margin-top: -4px;
}

.scale-row { display: flex; flex-wrap: wrap; align-items: center; gap: 10px; }
select {
  background: var(--panel-2);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 8px 10px;
  font-size: 14px;
}
select:disabled { opacity: 0.45; cursor: not-allowed; }

input[type="text"] {
  background: var(--panel-2);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 9px 12px;
  font-size: 14px;
  width: 100%;
}
input[type="text"]:focus {
  outline: none;
  border-color: var(--accent);
}
input[type="text"]::placeholder { color: var(--muted); opacity: 0.7; }
.checkbox {
  display: flex !important;
  flex-direction: row !important;
  align-items: center;
  gap: 6px;
  font-weight: 400 !important;
  font-size: 13px !important;
  color: var(--muted);
  cursor: pointer;
}
.checkbox input { accent-color: var(--accent); }

.control-actions { display: flex; flex-direction: column; gap: 8px; }

/* 버튼 */
.btn {
  border: 1px solid var(--border);
  background: var(--panel-2);
  color: var(--text);
  padding: 10px 14px;
  border-radius: 10px;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  transition: filter 0.12s, background 0.12s, border-color 0.12s;
}
.btn:hover { filter: brightness(1.12); }
.btn-primary { background: var(--accent-2); border-color: var(--accent-2); color: #fff; }
.btn-ghost { background: transparent; }
.btn-sm { padding: 6px 10px; font-size: 13px; }

/* 결과 */
.results {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  min-height: 300px;
}
.results-head {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 12px;
  margin-bottom: 18px;
}
.results-head strong { font-size: 22px; color: var(--accent); }
.results-actions { display: flex; gap: 8px; flex-wrap: wrap; }
.muted { color: var(--muted); font-size: 13px; }

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
  gap: 14px;
}

.piece {
  border: 1px solid var(--border);
  border-radius: 12px;
  overflow: hidden;
  background: var(--panel-2);
  transition: border-color 0.12s, transform 0.1s;
  position: relative;
}
.piece.selected { border-color: var(--accent); box-shadow: 0 0 0 1px var(--accent); }
.piece .thumb {
  aspect-ratio: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 12px;
  background-image:
    linear-gradient(45deg, var(--checker-a) 25%, transparent 25%),
    linear-gradient(-45deg, var(--checker-a) 25%, transparent 25%),
    linear-gradient(45deg, transparent 75%, var(--checker-a) 75%),
    linear-gradient(-45deg, transparent 75%, var(--checker-a) 75%);
  background-size: 16px 16px;
  background-position: 0 0, 0 8px, 8px -8px, -8px 0;
  background-color: var(--checker-b);
  cursor: pointer;
}
.piece .thumb img { max-width: 100%; max-height: 100%; image-rendering: auto; }
.piece .meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 8px 10px;
  gap: 8px;
  border-top: 1px solid var(--border);
}
.piece .meta .dim { font-size: 12px; color: var(--muted); font-variant-numeric: tabular-nums; }
.piece .meta button {
  background: transparent;
  border: none;
  color: var(--accent);
  cursor: pointer;
  font-size: 13px;
  padding: 2px 6px;
  border-radius: 6px;
}
.piece .meta button:hover { background: rgba(108, 140, 255, 0.12); }
.piece .check {
  position: absolute;
  top: 8px;
  left: 8px;
  width: 20px;
  height: 20px;
  accent-color: var(--accent);
  cursor: pointer;
}

/* 상태 */
.status {
  margin-top: 20px;
  padding: 14px 18px;
  border-radius: 10px;
  background: var(--panel);
  border: 1px solid var(--border);
  color: var(--muted);
  font-size: 14px;
}
.status.error { border-color: var(--danger); color: #ffb4b4; }

.hidden { display: none !important; }

/* ===== 콘텐츠 섹션 (소개/사용법/FAQ) ===== */
.content-section {
  margin-top: 48px;
  padding: 28px;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
}
.content-section h2 {
  margin: 0 0 14px;
  font-size: 22px;
  letter-spacing: -0.3px;
}
.content-section > p {
  color: var(--muted);
  line-height: 1.75;
  margin: 0 0 10px;
}
.content-section strong { color: var(--text); }

.feature-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 14px;
  margin-top: 18px;
}
.feature {
  background: var(--panel-2);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 16px;
}
.feature h3 { margin: 0 0 8px; font-size: 15px; }
.feature p { margin: 0; font-size: 13px; color: var(--muted); line-height: 1.65; }

.steps { margin: 0; padding-left: 20px; color: var(--muted); line-height: 1.9; }
.steps li { margin-bottom: 6px; }
.steps strong { color: var(--text); }

#faq details {
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--panel-2);
  padding: 0 16px;
  margin-bottom: 10px;
}
#faq summary {
  cursor: pointer;
  padding: 14px 0;
  font-weight: 600;
  font-size: 14px;
  list-style: none;
}
#faq summary::before { content: "❓ "; }
#faq details[open] summary { border-bottom: 1px solid var(--border); }
#faq details p { color: var(--muted); line-height: 1.7; font-size: 14px; }

/* ===== 푸터 ===== */
.site-footer {
  max-width: 1180px;
  margin: 40px auto 0;
  padding: 24px 28px 36px;
  border-top: 1px solid var(--border);
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 12px;
}
.site-footer p { margin: 0; color: var(--muted); font-size: 13px; }
.site-footer nav { display: flex; gap: 16px; }
.site-footer a { color: var(--muted); font-size: 13px; text-decoration: none; }
.site-footer a:hover { color: var(--accent); }

/* ===== 개인정보처리방침 ===== */
.legal { max-width: 760px; }
.legal h2 { font-size: 24px; margin: 0 0 6px; }
.legal h3 { font-size: 16px; margin: 28px 0 8px; }
.legal p { color: var(--muted); line-height: 1.8; margin: 0 0 8px; }
.legal strong { color: var(--text); }
.legal a { color: var(--accent); }

/* ===== 모바일 최적화 (파일 끝에 두어 항상 우선 적용) ===== */
@media (max-width: 900px) {
  /* 컨트롤을 고정하지 않고 자연스럽게 스크롤 */
  .controls { position: static; top: auto; }
}

/* 폰 세로 화면 */
@media (max-width: 600px) {
  main { padding: 16px; }
  .topbar { padding: 16px; }
  .brand h1 { font-size: 18px; }
  .brand p { font-size: 12px; }
  .drop-zone { padding: 40px 16px; }
  .workspace { gap: 16px; }
  .controls { padding: 16px; gap: 16px; }
  .results { padding: 16px; }
  /* 결과 액션 버튼을 가로로 꽉 차게 */
  .results-actions { width: 100%; }
  .results-actions .btn { flex: 1; }
  #downloadSelected { flex-basis: 100%; }
  /* 썸네일 2열 */
  .grid { grid-template-columns: repeat(2, 1fr); gap: 10px; }
  /* 터치 타깃 확대 */
  .piece .check { width: 24px; height: 24px; }
  .piece .meta button { padding: 6px 8px; }
  select { padding: 10px; font-size: 15px; }
}