:root {
    color-scheme: light;
    --md-primary: #0b57d0;
    --md-on-primary: #fff;
    --md-primary-container: #d3e3fd;
    --md-on-primary-container: #041e49;
    --md-secondary-container: #c2e7ff;
    --md-on-secondary-container: #001d35;
    --md-surface: #f8fafd;
    --md-surface-container: #f0f4f9;
    --md-surface-container-high: #e9eef6;
    --md-surface-bright: #fff;
    --md-on-surface: #1f1f1f;
    --md-on-surface-variant: #444746;
    --md-outline: #747775;
    --md-outline-variant: #c4c7c5;
    --md-success: #146c2e;
    --md-success-container: #c4eed0;
    --md-error: #b3261e;
    --md-error-container: #f9dedc;
    --md-shadow: 0 1px 2px rgba(60, 64, 67, .1), 0 1px 3px 1px rgba(60, 64, 67, .08);
    --md-shadow-raised: 0 2px 6px 2px rgba(60, 64, 67, .15);
    --ease: cubic-bezier(.2, 0, 0, 1);
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
    margin: 0;
    min-width: 320px;
    background: var(--md-surface);
    color: var(--md-on-surface);
    font-family: "Roboto", Arial, sans-serif;
    font-size: 15px;
    line-height: 1.55;
    -webkit-font-smoothing: antialiased;
}

a { color: var(--md-primary); text-decoration: none; }
a:hover { text-decoration: underline; }

button, input, textarea, select { font: inherit; }

input, textarea, select {
    width: 100%;
    min-height: 52px;
    border: 1px solid var(--md-outline);
    border-radius: 12px;
    padding: 13px 15px;
    background: var(--md-surface-bright);
    color: var(--md-on-surface);
    outline: none;
    transition: border-color .2s var(--ease), box-shadow .2s var(--ease), background .2s var(--ease);
}

input:hover, textarea:hover, select:hover { border-color: var(--md-on-surface); }
input:focus, textarea:focus, select:focus {
    border-color: var(--md-primary);
    box-shadow: inset 0 0 0 1px var(--md-primary);
}
input[readonly] { background: var(--md-surface-container); color: var(--md-on-surface-variant); }
textarea { resize: vertical; min-height: 120px; }
select { cursor: pointer; }

label { color: var(--md-on-surface-variant); font-weight: 600; }
label small, td small { display: block; margin-top: 4px; color: var(--md-on-surface-variant); font-weight: 400; }

fieldset {
    border: 1px solid var(--md-outline-variant);
    border-radius: 20px;
    padding: 20px;
}
legend { padding: 0 8px; font-family: "Roboto", sans-serif; font-weight: 600; }
hr { margin: 24px 0; border: 0; border-top: 1px solid var(--md-outline-variant); }

.material-symbols-rounded {
    font-size: 21px;
    line-height: 1;
    font-variation-settings: "FILL" 0, "wght" 400, "GRAD" 0, "opsz" 24;
}

.topbar {
    position: sticky;
    top: 0;
    z-index: 50;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 24px;
    min-height: 72px;
    padding: 10px clamp(16px, 3vw, 36px);
    background: rgba(248, 250, 253, .94);
    border-bottom: 1px solid transparent;
    backdrop-filter: blur(14px);
}

.topbar.scrolled { border-bottom-color: var(--md-outline-variant); box-shadow: 0 1px 2px rgba(60,64,67,.08); }

.brand {
    display: inline-flex;
    align-items: center;
    gap: 12px;
    color: #3c4043;
    font-family: "Roboto", sans-serif;
    font-size: 20px;
    font-weight: 600;
    letter-spacing: -.3px;
    white-space: nowrap;
}
.brand:hover { text-decoration: none; }
.brand-mark {
    display: grid;
    width: 42px;
    height: 42px;
    place-items: center;
    border-radius: 13px;
    background: linear-gradient(135deg, #0b57d0, #4285f4);
    color: #fff;
    font-size: 25px;
    box-shadow: var(--md-shadow);
}

.nav { display: flex; align-items: center; gap: 4px; }
.nav-link {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    min-height: 44px;
    padding: 0 16px;
    border-radius: 22px;
    color: var(--md-on-surface-variant);
    font-weight: 600;
    transition: background .2s var(--ease), color .2s var(--ease);
}
.nav-link:hover { background: var(--md-surface-container-high); text-decoration: none; }
.nav-link.active { background: var(--md-primary-container); color: var(--md-on-primary-container); }
.nav-link.active .material-symbols-rounded { font-variation-settings: "FILL" 1, "wght" 500, "GRAD" 0, "opsz" 24; }
.nav-divider { width: 1px; height: 32px; margin: 0 8px; background: var(--md-outline-variant); }
.user-chip { display: inline-flex; align-items: center; gap: 9px; margin: 0 4px; color: var(--md-on-surface-variant); font-weight: 500; }
.avatar { display: grid; width: 36px; height: 36px; place-items: center; border-radius: 50%; background: #e8def8; color: #4a4458; font-family: "Roboto", sans-serif; font-weight: 700; }

.icon-button, .link-button {
    display: inline-grid;
    width: 44px;
    height: 44px;
    padding: 0;
    place-items: center;
    border: 0;
    border-radius: 50%;
    background: transparent;
    color: var(--md-on-surface-variant);
    cursor: pointer;
}
.icon-button:hover, .link-button:hover { background: var(--md-surface-container-high); }

.page { width: min(1240px, calc(100% - 48px)); margin: 38px auto 64px; }
.page-header { display: flex; align-items: flex-start; justify-content: space-between; gap: 24px; margin-bottom: 28px; }
.page-header h1, .auth-shell h1 { margin: 0; font-family: "Roboto", sans-serif; font-size: clamp(2rem, 3vw, 2.55rem); font-weight: 500; line-height: 1.16; letter-spacing: -.7px; }
.page-header p:last-child { margin-bottom: 0; }
.eyebrow { margin: 0 0 7px; color: var(--md-primary); font-size: 12px; font-weight: 700; letter-spacing: .9px; text-transform: uppercase; }
.muted { color: var(--md-on-surface-variant); }

.panel, .card, .stat {
    background: var(--md-surface-bright);
    border: 1px solid var(--md-outline-variant);
    border-radius: 24px;
    box-shadow: none;
    transition: box-shadow .2s var(--ease), transform .2s var(--ease), border-color .2s var(--ease);
}
.panel { padding: 28px; }
.card:hover { border-color: transparent; box-shadow: var(--md-shadow-raised); transform: translateY(-2px); }

.auth-shell { min-height: calc(100vh - 180px); display: grid; grid-template-columns: minmax(0, 1fr) minmax(340px, 460px); gap: clamp(40px, 8vw, 110px); align-items: center; }
.auth-shell > div:first-child { max-width: 620px; }
.auth-shell > div:first-child::before {
    content: "school";
    display: grid;
    width: 72px;
    height: 72px;
    margin-bottom: 28px;
    place-items: center;
    border-radius: 22px;
    background: var(--md-primary-container);
    color: var(--md-primary);
    font-family: "Material Symbols Rounded";
    font-size: 38px;
}
.auth-panel { display: grid; gap: 20px; padding: 32px; box-shadow: var(--md-shadow); }
.auth-panel label, .form-stack label, .form-panel label { display: grid; gap: 8px; }
.hint-box { display: inline-grid; gap: 4px; margin-top: 24px; padding: 16px 20px; border-radius: 16px; background: var(--md-secondary-container); color: var(--md-on-secondary-container); }

.alert { display: flex; align-items: flex-start; gap: 12px; margin-bottom: 22px; padding: 16px 18px; border-radius: 16px; font-weight: 500; }
.alert ul { margin: 7px 0 0 20px; padding: 0; font-weight: 400; }
.alert-success { background: var(--md-success-container); color: var(--md-success); }
.alert-error { background: var(--md-error-container); color: var(--md-error); }
.alert > .material-symbols-rounded { margin-top: 2px; font-variation-settings: "FILL" 1, "wght" 400, "GRAD" 0, "opsz" 24; }

.button {
    position: relative;
    isolation: isolate;
    overflow: hidden;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    min-height: 44px;
    padding: 0 22px;
    border: 1px solid transparent;
    border-radius: 22px;
    background: transparent;
    cursor: pointer;
    color: var(--md-primary);
    font-family: "Roboto", sans-serif;
    font-weight: 600;
    letter-spacing: .1px;
    text-decoration: none;
    white-space: nowrap;
    transition: box-shadow .2s var(--ease), background .2s var(--ease), transform .12s var(--ease);
}
.button:hover { text-decoration: none; box-shadow: var(--md-shadow); }
.button:active { transform: scale(.98); }
.button.primary { background: var(--md-primary); color: var(--md-on-primary); }
.button.primary:hover { background: #0842a0; }
.button.secondary { border-color: var(--md-outline); background: transparent; color: var(--md-primary); }
.button.secondary:hover { background: rgba(11,87,208,.08); }
.button.danger { background: var(--md-error-container); color: var(--md-error); }
.button.small { min-height: 36px; padding: 0 15px; border-radius: 18px; font-size: 13px; }
.button .material-symbols-rounded { font-size: 19px; }
.ripple { position: absolute; z-index: -1; border-radius: 50%; background: currentColor; opacity: .16; transform: scale(0); animation: ripple .55s linear; pointer-events: none; }
@keyframes ripple { to { opacity: 0; transform: scale(4); } }

.actions, .form-actions, .card-actions, .table-actions { display: flex; align-items: center; flex-wrap: wrap; gap: 10px; }
.form-actions { margin-top: 4px; }
.form-panel, .form-stack { display: grid; gap: 22px; max-width: 900px; }

.stats-grid { display: grid; grid-template-columns: repeat(5, minmax(0, 1fr)); gap: 14px; margin-bottom: 24px; }
.stat { position: relative; min-height: 150px; padding: 22px; background: var(--md-surface-container); border-color: transparent; }
.stat:hover { background: var(--md-primary-container); }
.stat > span:not(.stat-icon) { display: block; margin-top: 17px; color: var(--md-on-surface-variant); font-weight: 500; }
.stat strong { display: block; margin-top: 2px; font-family: "Roboto", sans-serif; font-size: 32px; font-weight: 500; }
.stat-icon { display: grid; width: 42px; height: 42px; place-items: center; border-radius: 13px; background: var(--md-surface-bright); color: var(--md-primary); font-size: 23px; font-variation-settings: "FILL" 1, "wght" 400, "GRAD" 0, "opsz" 24; }

.grid-two { display: grid; grid-template-columns: minmax(0, 1.15fr) minmax(320px, .85fr); gap: 20px; }
.section-title, .card-head, .meta-row { display: flex; align-items: flex-start; justify-content: space-between; gap: 16px; }
.section-title { align-items: center; margin-bottom: 18px; }
.section-title h2, .card h2, .panel h2 { margin: 0; font-family: "Roboto", sans-serif; font-size: 19px; font-weight: 600; }

.list { display: grid; gap: 4px; }
.list-item { display: flex; align-items: center; justify-content: space-between; gap: 14px; padding: 14px 16px; border-radius: 14px; color: var(--md-on-surface); transition: background .18s var(--ease); }
.list-item:hover { background: var(--md-surface-container); text-decoration: none; }
.list-item small, .meta-row { color: var(--md-on-surface-variant); font-size: 13px; }
.list-item small { display: block; margin-top: 2px; }

.cards { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 18px; margin-bottom: 24px; }
.card { display: grid; gap: 18px; min-height: 220px; padding: 24px; }
.card p { margin: 0; color: var(--md-on-surface-variant); }
.card-actions { align-self: end; }
.meta-row { flex-wrap: wrap; justify-content: flex-start; gap: 8px 18px; }
.meta-row span { display: inline-flex; align-items: center; }

.badge { display: inline-flex; align-items: center; min-height: 30px; padding: 4px 12px; border-radius: 15px; font-size: 12px; font-weight: 700; white-space: nowrap; }
.badge-green { background: var(--md-success-container); color: var(--md-success); }
.badge-muted { background: var(--md-surface-container-high); color: var(--md-on-surface-variant); }

.checkbox-grid { display: grid; grid-template-columns: repeat(6, minmax(80px, 1fr)); gap: 9px; }
.checkbox, .toggle { display: flex !important; align-items: center; gap: 10px !important; cursor: pointer; }
.checkbox input, .toggle input { width: 18px; min-height: 18px; margin: 0; accent-color: var(--md-primary); }
.checkbox { padding: 10px 12px; border: 1px solid var(--md-outline-variant); border-radius: 12px; background: var(--md-surface-bright); }
.checkbox:has(input:checked) { border-color: var(--md-primary); background: var(--md-primary-container); color: var(--md-on-primary-container); }
.toggle { width: fit-content; padding: 14px 18px; border-radius: 16px; background: var(--md-surface-container); }

.table-panel { margin-top: 22px; padding: 8px 12px; overflow-x: auto; }
table { width: 100%; border-collapse: collapse; }
th, td { padding: 16px 14px; border-bottom: 1px solid var(--md-outline-variant); text-align: left; vertical-align: top; }
th { color: var(--md-on-surface-variant); font-size: 12px; font-weight: 700; letter-spacing: .55px; text-transform: uppercase; }
tbody tr { transition: background .16s var(--ease); }
tbody tr:hover { background: var(--md-surface-container); }
tbody tr:last-child td { border-bottom: 0; }

.detail-panel { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 16px; margin-bottom: 22px; background: var(--md-surface-container); border-color: transparent; }
.detail-panel > div { padding: 8px; }
.detail-panel p { grid-column: 1 / -1; margin: 0; padding: 8px; }
.detail-panel.compact { grid-template-columns: repeat(2, minmax(0, 1fr)); padding: 0; border: 0; background: transparent; }
.label { display: block; margin-bottom: 5px; color: var(--md-on-surface-variant); font-size: 12px; font-weight: 600; letter-spacing: .3px; }

.grade-form, .grade-result, .upload-box, .submission-summary { display: grid; gap: 10px; }
.grade-form { min-width: 220px; }
.grade-form input { max-width: 120px; }
.grade-result { min-width: 180px; }
.grade-result p { margin: 0; color: var(--md-on-surface-variant); }
.locked-submission { display: grid; gap: 4px; padding: 16px 18px; border-radius: 16px; background: var(--md-success-container); color: var(--md-success); }

.assignment-attachment { display: grid; gap: 14px; padding: 20px; border-radius: 18px; background: var(--md-surface-container); }
.attachment-head, .current-attachment { display: flex; align-items: center; justify-content: space-between; flex-wrap: wrap; gap: 12px; }
.attachment-preview { width: 100%; max-height: 480px; border-radius: 16px; background: #202124; }
.image-preview { object-fit: contain; }
.video-preview { display: block; }
.attachment-download-note { margin: 0; }
.file-name { color: var(--md-on-surface-variant); }
.score-box { display: flex; align-items: baseline; gap: 8px; }
.score-box strong { color: var(--md-success); font-family: "Roboto", sans-serif; font-size: 42px; font-weight: 500; }

.copy-field { display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 10px; margin: 16px 0; }
.empty { color: var(--md-on-surface-variant); text-align: center; padding: 28px; }
.pagination { margin-top: 20px; }
.pagination nav { display: flex; justify-content: space-between; gap: 12px; }

.snackbar { position: fixed; z-index: 100; left: 50%; bottom: 28px; max-width: min(90vw, 480px); padding: 13px 20px; border-radius: 8px; background: #303030; color: #fff; box-shadow: var(--md-shadow-raised); opacity: 0; transform: translate(-50%, 20px); pointer-events: none; transition: opacity .2s var(--ease), transform .2s var(--ease); }
.snackbar.show { opacity: 1; transform: translate(-50%, 0); }

@media (max-width: 1000px) {
    .nav-user, .nav-divider { display: none; }
    .stats-grid { grid-template-columns: repeat(3, minmax(0, 1fr)); }
    .checkbox-grid { grid-template-columns: repeat(4, minmax(80px, 1fr)); }
}

@media (max-width: 760px) {
    .topbar { align-items: flex-start; flex-direction: column; gap: 10px; }
    .nav { width: 100%; overflow-x: auto; padding-bottom: 3px; }
    .nav-link { flex: 0 0 auto; padding: 0 13px; }
    .nav form { margin-left: auto; }
    .user-chip { display: none; }
    .page { width: min(100% - 28px, 1240px); margin-top: 28px; }
    .auth-shell, .grid-two { grid-template-columns: 1fr; }
    .auth-shell { gap: 32px; }
    .auth-shell > div:first-child::before { width: 56px; height: 56px; margin-bottom: 18px; border-radius: 17px; font-size: 30px; }
    .stats-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
    .cards { grid-template-columns: 1fr; }
    .checkbox-grid { grid-template-columns: repeat(3, minmax(70px, 1fr)); }
    .detail-panel { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

@media (max-width: 520px) {
    .brand { font-size: 18px; }
    .brand-mark { width: 38px; height: 38px; }
    .page-header, .section-title, .card-head { flex-direction: column; align-items: stretch; }
    .page-header .actions, .page-header > .button { width: 100%; }
    .page-header .button { flex: 1; }
    .stats-grid { grid-template-columns: 1fr; }
    .stat { min-height: 124px; }
    .checkbox-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
    .detail-panel, .detail-panel.compact { grid-template-columns: 1fr; }
    .copy-field { grid-template-columns: 1fr; }
    .auth-panel, .panel { padding: 22px; }
    .table-panel { padding: 4px; }
}

@media (prefers-reduced-motion: reduce) {
    *, *::before, *::after { scroll-behavior: auto !important; animation-duration: .01ms !important; transition-duration: .01ms !important; }
}