*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
:root {
  --bg: #f8f9fa;
  --text: #333;
  --h1: #444;
  --input-bg: #fff;
  --input-border: #e0e0e0;
  --input-focus: #90caf9;
  --no-results: #888;
  --panel-bg: #fff;
  --panel-shadow: rgba(0,0,0,.2);
  --backdrop: rgba(0,0,0,.25);
  --close-hover-bg: #f0f0f0;
  --close-hover-text: #333;
  --subtitle: #666;
  --label: #888;
  --sel-outline: #333;
  --cat-label: #888;
}
.dark {
  --bg: #1a1a2e;
  --text: #fff;
  --h1: #eee;
  --input-bg: #2a2a3e;
  --input-border: #444;
  --input-focus: #7c5cbf;
  --no-results: #999;
  --panel-bg: #1e1e32;
  --panel-shadow: rgba(0,0,0,.6);
  --backdrop: rgba(0,0,0,.55);
  --close-hover-bg: #3a3a4e;
  --close-hover-text: #fff;
  --subtitle: #ddd;
  --label: #ccc;
  --sel-outline: #7c5cbf;
  --cat-label: #ccc;
}
body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: var(--bg); color: var(--text);
  display: flex; flex-direction: column; align-items: center; padding: 20px; min-height: 100vh;
  transition: background .3s, color .3s;
}
h1 { font-size: 1.5rem; font-weight: 600; margin-bottom: 16px; color: var(--h1); }
.search-wrapper { position: relative; width: 100%; max-width: 400px; margin-bottom: 20px; }
.search-wrapper input {
  width: 100%; padding: 10px 16px; border: 2px solid var(--input-border); border-radius: 8px;
  font-size: 1rem; outline: none; transition: border-color .2s;
  background: var(--input-bg); color: var(--text);
}
.search-wrapper input:focus { border-color: var(--input-focus); }
#no-results { display: none; text-align: center; padding: 40px; color: var(--no-results); font-size: 1.1rem; }
#table-wrapper {
  position: relative; width: 100%; max-width: 1200px;
  display: flex; justify-content: center; gap: 0;
}
#periodic-table {
  display: grid;
  grid-template-columns: repeat(18, minmax(52px, 1fr));
  gap: 3px; padding: 4px;
  transition: opacity .3s;
}
.element {
  display: flex; flex-direction: column; align-items: center; justify-content: center;
  border-radius: 6px; cursor: pointer; user-select: none;
  padding: 4px 2px; min-height: 62px;
  transition: transform .15s, box-shadow .15s, opacity .3s;
  position: relative;
}
.element:hover { transform: translateY(-2px); box-shadow: 0 4px 12px rgba(0,0,0,.12); }
.element .number { font-size: .6rem; opacity: .6; line-height: 1; }
.element .symbol { font-size: 1.05rem; font-weight: 700; line-height: 1.2; }
.element .ename { font-size: .55rem; opacity: .8; line-height: 1; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; max-width: 100%; }
.element.hidden { opacity: .12; pointer-events: none; }
.element.selected { outline: 3px solid var(--sel-outline); outline-offset: 1px; z-index: 2; }
#detail-panel {
  display: none;
  position: fixed; top: 50%; left: 50%; transform: translate(-50%, -50%);
  width: 360px; max-width: 90vw;
  background: var(--panel-bg); border-radius: 12px; box-shadow: 0 8px 40px var(--panel-shadow);
  padding: 24px; z-index: 100; opacity: 0; transition: opacity .25s;
}
#detail-panel.open { display: block; opacity: 1; }
#detail-backdrop {
  display: none; position: fixed; inset: 0; background: var(--backdrop); z-index: 99;
}
#detail-backdrop.open { display: block; }
#detail-panel .close-btn {
  position: absolute; top: 12px; right: 12px;
  background: none; border: none; font-size: 1.3rem; cursor: pointer; color: var(--label);
  width: 28px; height: 28px; border-radius: 50%; display: flex; align-items: center; justify-content: center;
}
#detail-panel .close-btn:hover { background: var(--close-hover-bg); color: var(--close-hover-text); }
#detail-panel .detail-header { display: flex; align-items: center; gap: 12px; margin-bottom: 16px; }
#detail-panel .detail-icon {
  width: 60px; height: 60px; border-radius: 8px;
  display: flex; flex-direction: column; align-items: center; justify-content: center;
  font-weight: 700; flex-shrink: 0;
}
#detail-panel .detail-icon .dsym { font-size: 1.4rem; line-height: 1.1; }
#detail-panel .detail-icon .dnum { font-size: .65rem; opacity: .7; line-height: 1; }
#detail-panel .detail-icon .dname { font-size: .6rem; opacity: .8; line-height: 1; }
#detail-panel .detail-header-info h2 { font-size: 1.2rem; margin-bottom: 2px; color: var(--text); }
#detail-panel .detail-header-info .dsubtitle { font-size: .85rem; color: var(--subtitle); }
#detail-panel .detail-body { display: grid; grid-template-columns: 1fr 1fr; gap: 8px 16px; }
#detail-panel .detail-body .dlabel { font-size: .7rem; color: var(--label); text-transform: uppercase; letter-spacing: .03em; }
#detail-panel .detail-body .dvalue { font-size: .9rem; font-weight: 500; margin-bottom: 4px; }

.category-label {
  font-size: .7rem; font-weight: 600; color: var(--cat-label); text-transform: uppercase; letter-spacing: .05em;
  display: flex; align-items: center; padding-left: 4px;
}

#header-row {
  display: flex; align-items: center; gap: 12px; margin-bottom: 16px; flex-wrap: wrap;
  width: 100%; max-width: 1200px; justify-content: center;
}
#theme-toggle {
  background: none; border: 2px solid var(--input-border); border-radius: 8px;
  font-size: 1.3rem; cursor: pointer; padding: 6px 12px;
  transition: border-color .2s; line-height: 1;
}
#theme-toggle:hover { border-color: var(--input-focus); }

@media (max-width: 800px) {
  #periodic-table { gap: 2px; }
  .element { min-height: 48px; padding: 2px 1px; }
  .element .number { font-size: .5rem; }
  .element .symbol { font-size: .85rem; }
  .element .ename { font-size: .45rem; }
}