:root{
  --bg-1:#0b0f14;
  --bg-2:#101826;
  --card-bg:rgba(255,255,255,0.06);
  --card-bg-hover:rgba(255,255,255,0.10);
  --card-border:rgba(255,255,255,0.16);
  --text:#e7ecf3;
  --muted:#a8b1bd;
  --accent:#5ab2ff;
  --shadow: 0 10px 25px rgba(0,0,0,0.35), inset 0 1px 0 rgba(255,255,255,0.04);
  --radius:16px;
}

/* Reset & base */
*{box-sizing:border-box}
html,body{height:100%}
body{
  margin:0;
  font-family: Inter, system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, "PingFang SC","Hiragino Sans GB","Noto Sans CJK SC","Source Han Sans SC","Microsoft YaHei", sans-serif;
  color:var(--text);
  background:
    radial-gradient(1200px 800px at 80% -10%, #204b7a55 0%, transparent 60%),
    radial-gradient(1600px 1000px at -10% 120%, #3a2a6e40 0%, transparent 60%),
    linear-gradient(180deg, var(--bg-1), var(--bg-2));
  -webkit-font-smoothing:antialiased;
  -moz-osx-font-smoothing:grayscale;
}

/* Layout */
.site-header{
  padding:48px 24px 8px;
  text-align:center;
}
.title{
  margin:0;
  font-weight:700;
  font-size: clamp(28px, 4.8vw, 56px);
  letter-spacing: 0.4px;
  line-height:1.1;
}
.subtitle{
  margin:10px 0 0;
  color:var(--muted);
  font-size: clamp(14px, 2vw, 18px);
}

/* Grade switch */
.grade-switch{
  display:flex;
  gap:10px;
  justify-content:center;
  padding:8px 24px 0;
}
.grade-btn{
  appearance:none;
  border:1px solid var(--card-border);
  background: var(--card-bg);
  color: var(--text);
  border-radius: 999px;
  padding:8px 14px;
  font-size:14px;
  font-weight:600;
  cursor:pointer;
  transition: background .2s ease, border-color .2s ease, transform .2s ease, box-shadow .2s ease;
}
.grade-btn:hover{
  background: var(--card-bg-hover);
  border-color: rgba(255,255,255,0.28);
  transform: translateY(-2px);
  box-shadow: 0 8px 20px rgba(0,0,0,0.35);
}
.grade-btn.is-active{
  color:#0a2034;
  background: linear-gradient(180deg, #77c4ff, #4aa5f3);
  border-color: rgba(90,178,255,0.5);
  box-shadow: 0 6px 16px rgba(90,178,255,0.45);
}

.container{
  width:min(1100px, 92vw);
  margin: 28px auto 40px;
  display:grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap:20px;
}

.card{
  position:relative;
  display:flex;
  align-items:flex-start;
  gap:16px;
  text-decoration:none;
  color:inherit;
  padding:22px 22px;
  border-radius: var(--radius);
  background: var(--card-bg);
  border:1px solid var(--card-border);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  box-shadow: var(--shadow);
  transform: translateY(0) translateZ(0);
  transition: transform .25s ease, box-shadow .25s ease, background .25s ease, border-color .25s ease;
  overflow:hidden;
  isolation:isolate;
}

.card::before{
  content:"";
  position:absolute;
  inset: -1px;
  border-radius: inherit;
  background:
    radial-gradient(120px 80px at 10% 0%, rgba(255,255,255,0.12), transparent 70%),
    radial-gradient(160px 100px at 90% 110%, rgba(90,178,255,0.22), transparent 75%);
  opacity:.7;
  pointer-events:none;
  z-index:0;
}

.card:hover{
  transform: translateY(-6px);
  background: var(--card-bg-hover);
  border-color: rgba(255,255,255,0.28);
  box-shadow: 0 18px 40px rgba(0,0,0,0.45), inset 0 1px 0 rgba(255,255,255,0.05);
}

.card:active{
  transform: translateY(-2px);
}

.card-badge{
  z-index:1;
  margin-top:2px;
  flex:0 0 auto;
  height:28px;
  padding:0 10px;
  border-radius:999px;
  display:inline-flex;
  align-items:center;
  justify-content:center;
  font-size:12px;
  font-weight:700;
  letter-spacing:.6px;
  color:#0a2034;
  background: linear-gradient(180deg, #77c4ff, #4aa5f3);
  box-shadow: 0 6px 16px rgba(90,178,255,0.45);
}

.card-body{
  z-index:1;
  flex:1 1 auto;
  min-width:0;
}

.card-title{
  margin:0 0 6px;
  font-size: clamp(16px, 2.2vw, 20px);
  font-weight:700;
  line-height:1.25;
  letter-spacing:.2px;
}

.card-desc{
  margin:0;
  color:var(--muted);
  font-size:14px;
  line-height:1.5;
}

.card-arrow{
  z-index:1;
  flex:0 0 auto;
  margin-left:auto;
  margin-top:4px;
  width:36px;
  height:36px;
  border-radius:10px;
  display:grid;
  place-items:center;
  font-size:18px;
  color:#b8d9ff;
  background: linear-gradient(180deg, rgba(90,178,255,0.16), rgba(90,178,255,0.06));
  border:1px solid rgba(90,178,255,0.28);
  transition: transform .25s ease, background .25s ease, color .25s ease;
}

.card:hover .card-arrow{
  transform: translateX(3px) translateY(-3px);
  color:#e9f4ff;
  background: linear-gradient(180deg, rgba(90,178,255,0.26), rgba(90,178,255,0.12));
}

/* Footer */
.site-footer{
  text-align:center;
  padding:16px 24px 40px;
  color:var(--muted);
  font-size:12px;
}

/* Dark-mode friendly defaults already used via palette */
@media (max-width:480px){
  .card{ padding:18px; gap:14px; }
  .card-arrow{ width:32px; height:32px; font-size:16px; }
}