:root {
    --bg: #f6f8fb;
    --card: #ffffff;
    --text: #111827;
    --muted: #6b7280;
    --border: #e5e7eb;
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
    --danger: #dc2626;
    --success: #15803d;
    --shadow: 0 18px 45px rgba(15, 23, 42, 0.08);
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    font-family: Arial, "Noto Sans Bengali", sans-serif;
    background: var(--bg);
    color: var(--text);
}

a {
    color: inherit;
    text-decoration: none;
}

.container {
    width: min(1120px, calc(100% - 32px));
    margin: 0 auto;
}

.site-header {
    background: rgba(255, 255, 255, 0.92);
    border-bottom: 1px solid var(--border);
    position: sticky;
    top: 0;
    z-index: 10;
    backdrop-filter: blur(10px);
}

.header-inner {
    min-height: 76px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 20px;
}

.brand {
    display: flex;
    align-items: center;
    gap: 12px;
}

.brand-mark {
    width: 42px;
    height: 42px;
    border-radius: 14px;
    display: inline-grid;
    place-items: center;
    background: var(--primary);
    color: #fff;
    font-weight: 800;
    font-size: 22px;
}

.brand small {
    display: block;
    color: var(--muted);
    font-size: 12px;
    margin-top: 2px;
}

.nav {
    display: flex;
    align-items: center;
    gap: 18px;
    font-size: 14px;
}

.nav a {
    color: #374151;
}

.nav-btn {
    padding: 10px 14px;
    border-radius: 999px;
    background: #eff6ff;
    color: var(--primary) !important;
    font-weight: 700;
}

.site-main {
    padding: 52px 0;
    min-height: calc(100vh - 150px);
}

.hero {
    display: grid;
    grid-template-columns: 1.5fr 0.9fr;
    gap: 28px;
    align-items: center;
}

.badge {
    display: inline-flex;
    padding: 8px 12px;
    background: #e0f2fe;
    color: #0369a1;
    border-radius: 999px;
    font-size: 13px;
    font-weight: 700;
    margin-bottom: 16px;
}

.hero h1 {
    font-size: clamp(34px, 5vw, 58px);
    line-height: 1.08;
    margin: 0 0 18px;
    letter-spacing: -1.2px;
}

.hero p {
    color: var(--muted);
    font-size: 18px;
    line-height: 1.8;
    max-width: 680px;
}

.hero-actions {
    display: flex;
    gap: 12px;
    margin-top: 26px;
    flex-wrap: wrap;
}

.btn {
    border: 0;
    cursor: pointer;
    border-radius: 14px;
    padding: 13px 18px;
    font-weight: 800;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    font-size: 15px;
}

.btn.primary {
    background: var(--primary);
    color: #fff;
}

.btn.primary:hover {
    background: var(--primary-dark);
}

.btn.secondary {
    background: #eef2ff;
    color: #1e3a8a;
}

.btn.full {
    width: 100%;
}

.hero-card,
.feature-card,
.page-card,
.solver-panel {
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: 24px;
    box-shadow: var(--shadow);
}

.hero-card {
    padding: 28px;
}

.hero-card h3 {
    margin-top: 0;
}

.hero-card li {
    margin: 12px 0;
    color: #374151;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 18px;
    margin-top: 34px;
}

.feature-card {
    padding: 24px;
}

.feature-card h3 {
    margin-top: 0;
}

.feature-card p,
.muted {
    color: var(--muted);
    line-height: 1.7;
}

.page-card {
    padding: 30px;
}

.page-card.narrow {
    max-width: 520px;
    margin: 0 auto;
}

.form {
    display: grid;
    gap: 18px;
    margin-top: 22px;
}

label {
    display: grid;
    gap: 8px;
    font-weight: 700;
}

input,
select,
textarea {
    width: 100%;
    border: 1px solid var(--border);
    border-radius: 14px;
    padding: 13px 14px;
    font: inherit;
    background: #fff;
}

textarea {
    resize: vertical;
}

.class-box {
    border: 1px solid var(--border);
    padding: 16px;
    border-radius: 16px;
    display: grid;
    gap: 10px;
    background: #f9fafb;
}

.check-row {
    display: flex;
    gap: 10px;
    align-items: center;
    font-weight: 600;
}

.check-row input {
    width: auto;
}

.check-row.disabled {
    opacity: 0.55;
}

.dashboard-top {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
    margin-bottom: 24px;
}

.dashboard-top h1 {
    margin: 0 0 8px;
}

.trial-pill {
    padding: 10px 14px;
    background: #ecfdf5;
    color: #047857;
    border-radius: 999px;
    font-weight: 800;
    white-space: nowrap;
}

.solver-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 22px;
}

.solver-panel {
    padding: 22px;
    display: grid;
    gap: 18px;
}

.notebook-output {
    min-height: 282px;
    background:
        linear-gradient(#fff 31px, #dbeafe 32px),
        #fff;
    background-size: 100% 32px;
    border: 1px solid #bfdbfe;
    border-radius: 16px;
    padding: 20px;
    line-height: 32px;
}

.notice {
    padding: 14px 16px;
    border-radius: 14px;
    margin-bottom: 20px;
    border: 1px solid var(--border);
    background: #fff;
}

.notice.success {
    color: var(--success);
    background: #f0fdf4;
    border-color: #bbf7d0;
}

.notice.error {
    color: var(--danger);
    background: #fef2f2;
    border-color: #fecaca;
}

.site-footer {
    padding: 24px 0;
    border-top: 1px solid var(--border);
    color: var(--muted);
    font-size: 14px;
}

@media (max-width: 820px) {
    .header-inner,
    .dashboard-top {
        align-items: flex-start;
        flex-direction: column;
    }

    .nav {
        flex-wrap: wrap;
    }

    .hero,
    .features-grid,
    .solver-grid {
        grid-template-columns: 1fr;
    }

    .site-main {
        padding: 32px 0;
    }
}


/* Step 2B additions */
.center {
    text-align: center;
}

.text-link {
    color: var(--primary);
    font-weight: 800;
    text-decoration: underline;
    text-underline-offset: 3px;
}

.account-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 14px;
    margin-bottom: 22px;
}

.mini-card {
    background: #fff;
    border: 1px solid var(--border);
    border-radius: 18px;
    padding: 16px;
    box-shadow: 0 10px 25px rgba(15, 23, 42, 0.04);
    display: grid;
    gap: 8px;
}

.mini-card strong {
    color: #374151;
    font-size: 13px;
    text-transform: uppercase;
    letter-spacing: 0.04em;
}

.mini-card span {
    color: var(--text);
    font-weight: 700;
}

.locked-area {
    opacity: 0.72;
}

button:disabled,
input:disabled,
select:disabled,
textarea:disabled {
    cursor: not-allowed;
    opacity: 0.72;
}

@media (max-width: 820px) {
    .account-grid {
        grid-template-columns: 1fr;
    }
}


/* Step 2C Admin Panel */
.admin-shell {
    display: grid;
    gap: 22px;
}

.admin-top {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 18px;
}

.admin-top h1 {
    margin: 0 0 8px;
}

.admin-stats-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 14px;
}

.stat-card,
.admin-card {
    background: #fff;
    border: 1px solid var(--border);
    border-radius: 20px;
    box-shadow: 0 14px 35px rgba(15, 23, 42, 0.06);
}

.stat-card {
    padding: 18px;
    display: grid;
    gap: 6px;
}

.stat-card strong {
    font-size: 30px;
    line-height: 1;
    color: var(--primary);
}

.stat-card span {
    color: var(--muted);
    font-weight: 700;
}

.admin-card {
    padding: 22px;
}

.admin-card h2 {
    margin-top: 0;
}

.admin-card-head {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
    margin-bottom: 14px;
}

.table-wrap {
    overflow-x: auto;
}

.admin-table {
    width: 100%;
    border-collapse: collapse;
    min-width: 900px;
}

.admin-table th,
.admin-table td {
    border-bottom: 1px solid var(--border);
    padding: 12px 10px;
    text-align: left;
    vertical-align: middle;
    font-size: 14px;
}

.admin-table th {
    color: #374151;
    background: #f9fafb;
    font-size: 13px;
    text-transform: uppercase;
    letter-spacing: 0.04em;
}

.btn.small {
    padding: 8px 11px;
    border-radius: 10px;
    font-size: 13px;
    background: #eef2ff;
    color: #1e3a8a;
}

.admin-filter-form {
    display: grid;
    grid-template-columns: minmax(220px, 1fr) 220px auto auto;
    gap: 12px;
    align-items: center;
}

.admin-edit-grid {
    display: grid;
    grid-template-columns: 0.9fr 1.1fr;
    gap: 18px;
    align-items: start;
}

@media (max-width: 920px) {
    .admin-top,
    .admin-card-head {
        align-items: flex-start;
        flex-direction: column;
    }

    .admin-stats-grid,
    .admin-edit-grid,
    .admin-filter-form {
        grid-template-columns: 1fr;
    }
}


/* Step 3A AI Solver */
.output-head {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
}

.output-head h3 {
    margin: 0;
}

.verification-badge {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 7px 10px;
    border-radius: 999px;
    font-size: 12px;
    font-weight: 900;
    text-transform: uppercase;
    letter-spacing: 0.04em;
    white-space: nowrap;
}

.muted-badge {
    background: #f3f4f6;
    color: #4b5563;
}

.checking-badge {
    background: #eff6ff;
    color: #1d4ed8;
}

.passed-badge {
    background: #ecfdf5;
    color: #047857;
}

.warning-badge {
    background: #fffbeb;
    color: #b45309;
}

.failed-badge {
    background: #fef2f2;
    color: #b91c1c;
}

.verification-message {
    margin-top: -8px;
    font-size: 13px;
    line-height: 1.5;
}

.solve-message {
    min-height: 22px;
    font-size: 14px;
    font-weight: 700;
}

.solve-message.success {
    color: var(--success);
}

.solve-message.error {
    color: var(--danger);
}

.small-note {
    font-size: 13px;
    margin: -6px 0 0;
}

.notebook-output {
    white-space: normal;
}

.notebook-output p {
    margin-top: 0;
}