:root {
  color-scheme: light dark;
  --bg-gradient-start: #f0f4f8;
  --bg-gradient-end: #e2e8f0;
  --text-color: #1e293b;
  --text-muted: #64748b;
  --panel-bg: rgba(255, 255, 255, 0.85);
  --panel-shadow: none;
  --bubble-bg: rgba(255, 255, 255, 0.95);
  --bubble-border: rgba(0, 0, 0, 0.08);
  --bubble-shadow: none;
  --bubble-hover-bg: rgba(255, 255, 255, 1);
  --bubble-hover-border: rgba(56, 189, 248, 0.6);
  --bubble-hover-shadow: none;
  --bubble-active-bg: rgba(224, 242, 254, 0.95);
  --bubble-active-border: #0ea5e9;
  --connector-stroke: rgba(148, 163, 184, 0.4);
  --btn-bg: #ffffff;
  --btn-border: rgba(0, 0, 0, 0.1);
  --btn-text: #334155;
  --btn-hover: #f8fafc;
  --toggle-bg: rgba(255, 255, 255, 0.9);
  --toggle-border: rgba(0, 0, 0, 0.1);
}

[data-theme="dark"] {
  --bg-gradient-start: #0f172a;
  --bg-gradient-end: #020617;
  --text-color: #f8fafc;
  --text-muted: #94a3b8;
  --panel-bg: rgba(15, 23, 42, 0.65);
  --panel-shadow: none;
  --bubble-bg: rgba(30, 41, 59, 0.95);
  --bubble-border: rgba(255, 255, 255, 0.1);
  --bubble-shadow: none;
  --bubble-hover-bg: rgba(30, 41, 59, 1);
  --bubble-hover-border: rgba(56, 189, 248, 0.4);
  --bubble-hover-shadow: none;
  --bubble-active-bg: rgba(14, 165, 233, 0.3);
  --bubble-active-border: #0ea5e9;
  --connector-stroke: rgba(71, 85, 105, 0.4);
  --btn-bg: #1e293b;
  --btn-border: rgba(255, 255, 255, 0.1);
  --btn-text: #e2e8f0;
  --btn-hover: #334155;
  --toggle-bg: rgba(30, 41, 59, 0.9);
  --toggle-border: rgba(255, 255, 255, 0.1);
}

* { box-sizing: border-box; }

body, html {
  margin: 0;
  min-height: 100vh;
  width: 100%;
}

body {
  display: flex;
  align-items: flex-start;
  justify-content: center;
  padding: 16px;
  font-family: Inter, system-ui, sans-serif;
  background: radial-gradient(circle at top, var(--bg-gradient-start) 0%, var(--bg-gradient-end) 100%);
  color: var(--text-color);
  transition: background 0.3s ease, color 0.3s ease;
}

.theme-toggle {
  position: fixed;
  top: 16px;
  right: 16px;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  border: 1px solid var(--toggle-border);
  background: var(--toggle-bg);
  font-size: 1.5rem;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  z-index: 100;
  transition: transform 0.2s ease, background 0.3s ease, border-color 0.3s ease;
  backdrop-filter: blur(8px);
}

.theme-toggle:hover {
  transform: scale(1.05);
}

.page-shell {
  width: 100%;
  max-width: 900px;
  margin: auto;
}

.brand-panel {
  text-align: center;
  padding: 48px 24px;
  border-radius: 28px;
  backdrop-filter: blur(12px);
  background: var(--panel-bg);
  box-shadow: 0 16px 40px var(--panel-shadow);
  transition: background 0.3s ease, box-shadow 0.3s ease;
}

.title-block {
  margin-bottom: 32px;
}

.main-logo {
  display: block;
  margin: 0 auto 24px auto;
  width: 128px;
  height: 128px;
  object-fit: cover;
  border-radius: 50%;
  border: 2px solid var(--bubble-border);
  box-shadow: 0 4px 16px var(--bubble-shadow);
  transition: transform 0.3s ease, border-color 0.3s ease;
}

.main-logo:hover {
  transform: scale(1.05);
  border-color: var(--bubble-hover-border);
}

#title {
  margin: 0;
  font-size: clamp(2.5rem, 8vw, 6rem);
  letter-spacing: -0.06em;
  line-height: 0.92;
  min-height: clamp(3rem, 10vw, 6.5rem);
  overflow: hidden;
  position: relative;
}

.subtitle {
  margin: 12px auto 0;
  color: var(--text-muted);
  font-size: clamp(0.875rem, 3vw, 1rem);
  transition: color 0.3s ease;
}

.bubble-area {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 18px;
  opacity: 0;
  transform: translateY(16px);
  transition: opacity 0.45s ease, transform 0.45s ease;
}

.bubble-area.visible {
  opacity: 1;
  transform: translateY(0);
}

.bubble-hint {
  margin: 0;
  color: var(--text-muted);
  font-size: 0.975rem;
  transition: color 0.3s ease;
}

.bubble-grid,
.subtree-grid {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 16px;
  width: 100%;
  max-width: 800px;
}

.tree-graph {
  position: relative;
  width: 100%;
}

.tree-body {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 16px;
  width: 100%;
}

.bubble,
.sub-bubble {
  flex: 1 1 160px;
  max-width: 240px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 10px;
  padding: 16px;
  border: 1px solid var(--bubble-border);
  border-radius: 24px;
  background: var(--bubble-bg);
  box-shadow: 0 4px 12px var(--bubble-shadow);
  color: inherit;
  cursor: pointer;
  transition: transform 0.3s ease, border-color 0.3s ease, background 0.3s ease, box-shadow 0.3s ease, opacity 0.25s ease;
  min-height: 120px;
}

.bubble:hover,
.sub-bubble:hover {
  transform: translateY(-4px);
  border-color: var(--bubble-hover-border);
  background: var(--bubble-hover-bg);
  box-shadow: 0 8px 24px var(--bubble-hover-shadow);
}

.bubble-icon,
.sub-bubble-icon {
  font-size: 2.2rem;
  flex-shrink: 0;
}

.bubble-text,
.sub-bubble-text {
  font-size: 0.95rem;
  font-weight: 600;
  text-align: center;
  flex-shrink: 0;
}

.sub-bubble-desc {
  width: 100%;
  display: grid;
  grid-template-rows: 0fr;
  transition: grid-template-rows 0.4s cubic-bezier(0.4, 0, 0.2, 1), margin-top 0.4s ease, opacity 0.4s ease;
  margin-top: 0;
  opacity: 0;
}

.sub-bubble-desc-inner {
  min-height: 0;
  overflow: hidden;
  font-size: 0.85rem;
  color: var(--text-muted);
  text-align: left;
  line-height: 1.5;
  padding: 8px 4px 0;
}

.sub-bubble-desc-inner a {
  color: inherit;
  text-decoration: underline;
  text-decoration-style: dashed;
}

.sub-bubble.expanded .sub-bubble-desc {
  grid-template-rows: 1fr;
  opacity: 1;
  margin-top: 10px;
}

.bubble.hidden {
  display: none !important;
}

.bubble[data-label="browsing"] { view-transition-name: bubble-browsing; }
.bubble[data-label="operatingsystems"] { view-transition-name: bubble-os; }
.bubble[data-label="marks"] { view-transition-name: bubble-marks; }
.bubble[data-label="goodpractices"] { view-transition-name: bubble-gp; }

.subtree-area.hidden {
  grid-template-rows: 0fr;
}

.bubble.active {
  border-color: var(--bubble-active-border);
  background: var(--bubble-active-bg);
  transform: scale(1.04);
}

.subtree-area {
  width: 100%;
  display: grid;
  grid-template-rows: 1fr;
  transition: grid-template-rows 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

.subtree-wrapper {
  overflow: hidden;
}

.connector {
  position: absolute;
  inset: 0;
  pointer-events: none;
  overflow: visible;
  z-index: -1;
}

.connector-path {
  stroke: var(--connector-stroke);
  stroke-width: 2.5;
  stroke-linecap: round;
  stroke-linejoin: round;
  transition: stroke 0.3s ease;
}


@media (max-width: 600px) {
  .brand-panel {
    padding: 32px 16px;
  }
  .bubble-grid,
  .subtree-grid {
    flex-direction: column;
    align-items: center;
  }
  .bubble, .sub-bubble {
    width: 100%;
    max-width: 320px;
    min-height: 100px;
    flex-basis: auto;
  }
  .bubble-icon, .sub-bubble-icon {
    font-size: 2.2rem;
  }
}

.news-panel {
  margin-top: 32px;
  padding: 32px 24px;
  border-radius: 28px;
  backdrop-filter: blur(12px);
  background: var(--panel-bg);
  box-shadow: 0 16px 40px var(--panel-shadow);
  transition: background 0.3s ease, box-shadow 0.3s ease;
  text-align: left;
}

.news-panel h2 {
  margin-top: 0;
  margin-bottom: 24px;
  font-size: 1.5rem;
  font-weight: 600;
  color: var(--text-color);
  border-bottom: 1px solid var(--bubble-border);
  padding-bottom: 12px;
}

.news-list {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.news-item {
  padding: 16px;
  border-radius: 16px;
  background: var(--bubble-bg);
  border: 1px solid var(--bubble-border);
  transition: background 0.3s ease, border-color 0.3s ease;
}

.news-meta {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 8px;
  font-size: 0.85rem;
  color: var(--text-muted);
}

.news-timeago {
  font-weight: 600;
  color: var(--bubble-active-border);
}

.news-content {
  margin: 0;
  font-size: 0.95rem;
  line-height: 1.5;
  color: var(--text-color);
}