:root{
    --bg: #f4f7fb;
    --card-bg: linear-gradient(180deg,#ffffff,#fbfdff);
    --muted: #6b7280;
    --accent: #3b82f6;
}

body {
    background: var(--bg);
    color: #0b1220;
    font-family: "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    margin: 0;
    padding: 28px 12px;
}

main {
    width: 100%;
    max-width: 1100px;
    margin: 0 auto;
}

h1 { font-size: 1.25rem; text-align: center; margin: 0 0 8px 0; }
h2 { font-size: 1rem; text-align: center; margin: 0 0 6px 0; }

.boards {
    position: relative;
    display: flex;
    gap: 24px;
}
.board { display: flex; flex-direction: column; }
.board .row { display: flex; }
.tile {
    border: 1px solid #333;
    width: 100px;
    height: 100px;
    position: relative;
    background: #fff;
}
.tile img { width: 100%; height: 100%; display: block; }
.tile-number {
    position: absolute; top: 6px; left: 6px; width: 20px; height: 20px;
    background: lightskyblue; border-radius: 50%; display: flex; align-items: center;
    justify-content: center; font-size: 10px; line-height: 1; z-index: 2; pointer-events: none;
}
.player .tile:empty { background: #000; }
.blurred { filter: blur(25px); opacity: 0.4; pointer-events: none; user-select: none; }

.controls { display: flex; justify-content: center; gap: 8px; margin-top: 12px; }

.submissions-container{
    display: flex;
    gap: 20px;
    flex-wrap: wrap;
    justify-content: center;
    margin: 18px 0 28px;
}
.class-block{
    flex: 1 1 300px;
    min-width: 220px;
    max-width: 360px;
    background: var(--card-bg);
    border-radius: 12px;
    padding: 14px;
    border: 1px solid rgba(15,23,42,0.06);
    box-shadow: 0 6px 18px rgba(15,23,42,0.06);
}
.class-block h3{ margin: 0 0 8px 0; font-size: 1.05rem; text-align: center; color: #0f172a; }
.student-grid{ display: grid; grid-template-columns: repeat(8, 1fr); gap: 8px; margin-top: 10px; }
.student-link{
    display: flex; align-items: center; justify-content: center; padding: 8px 6px;
    border-radius: 8px; text-decoration: none; color: #07203a; background: #fff;
    border: 1px solid rgba(15,23,42,0.06); font-weight: 600;
    transition: transform .18s ease, box-shadow .18s ease, background .18s ease;
    box-shadow: 0 2px 6px rgba(2,6,23,0.04);
}
.student-link:hover{
    transform: translateY(-6px);
    background: linear-gradient(180deg,#eef7ff,#e6f2ff);
    border-color: rgba(59,130,246,0.22);
    box-shadow: 0 10px 24px rgba(59,130,246,0.09);
}
.student-link:active{ transform: translateY(-2px); }

@media (max-width: 1000px){ .student-grid{ grid-template-columns: repeat(6,1fr); } }
@media (max-width: 720px){ .student-grid{ grid-template-columns: repeat(4,1fr); } }
@media (max-width: 420px){ .student-grid{ grid-template-columns: repeat(3,1fr); } .class-block{ padding:10px } }

.error{ color: var(--muted); background: #fff; padding: 10px; border-radius: 8px; border: 1px solid rgba(0,0,0,0.04); }