:root {
    --background: #f4f6f8;

    --surface: #ffffff;
    --surface-soft: #f8fafc;

    --text: #1f2937;
    --text-muted: #6b7280;

    --border: #e2e8f0;

    --primary: #2563eb;
    --primary-hover: #1d4ed8;
    --primary-soft: #eff6ff;
    --primary-soft-hover: #dbeafe;
    --primary-border: #bfdbfe;

    --success: #15803d;
    --success-background: #f0fdf4;
    --success-border: #bbf7d0;

    --danger: #b91c1c;
    --danger-background: #fef2f2;
    --danger-border: #fecaca;

    --radius-small: 8px;
    --radius: 12px;
    --radius-large: 16px;

    --shadow:
        0 1px 2px rgba(0, 0, 0, 0.04),
        0 6px 20px rgba(0, 0, 0, 0.06);
}


/* ==================================================
   Base
================================================== */

* {
    box-sizing: border-box;
}

body {
    min-height: 100vh;
    margin: 0;

    background: var(--background);
    color: var(--text);

    font-family:
        system-ui,
        -apple-system,
        BlinkMacSystemFont,
        "Segoe UI",
        sans-serif;

    line-height: 1.5;
}

button,
input {
    font: inherit;
}

a {
    color: inherit;
}

.page-container {
    width: min(960px, calc(100% - 2rem));
    margin: 0 auto;
    padding: 3rem 0;
}

.page-subtitle {
    margin: 0.5rem 0 0;

    color: var(--text-muted);
    font-size: 0.95rem;
}


/* ==================================================
   Shared layout
================================================== */

.centered-page,
.auth-page {
    min-height: calc(100vh - 6rem);

    display: flex;
    align-items: center;
    justify-content: center;
}


/* ==================================================
   Cards
================================================== */

.auth-card,
.task-card,
.results-card {
    width: 100%;
    padding: 2.5rem;

    background: var(--surface);

    border: 1px solid var(--border);
    border-radius: var(--radius-large);

    box-shadow: var(--shadow);
}

.auth-card {
    max-width: 420px;
}

.task-card {
    max-width: 560px;
}

.results-card {
    max-width: 720px;
}


/* ==================================================
   Buttons
================================================== */

button,
.button {
    display: inline-flex;
    align-items: center;
    justify-content: center;

    padding: 0.8rem 1.2rem;

    background: var(--primary);
    color: #ffffff;

    border: 0;
    border-radius: var(--radius-small);

    font-weight: 600;
    text-decoration: none;

    cursor: pointer;

    transition:
        background-color 0.15s ease,
        transform 0.05s ease;
}

button:hover,
.button:hover {
    background: var(--primary-hover);
}

button:active,
.button:active {
    transform: translateY(1px);
}

button:focus-visible,
.button:focus-visible {
    outline: 3px solid rgba(37, 99, 235, 0.25);
    outline-offset: 2px;
}


/* ==================================================
   Forms
================================================== */

.form-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.form-group label {
    font-size: 0.9rem;
    font-weight: 600;
}

.form-help {
    margin: 0;

    color: var(--text-muted);
    font-size: 0.8rem;
}

input[type="text"],
input[type="password"] {
    width: 100%;
    padding: 0.8rem 0.9rem;

    background: var(--surface);
    color: var(--text);

    border: 1px solid var(--border);
    border-radius: var(--radius-small);

    transition:
        border-color 0.15s ease,
        box-shadow 0.15s ease;
}

input[type="text"]:focus,
input[type="password"]:focus {
    border-color: var(--primary);

    outline: none;
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.14);
}


/* ==================================================
   File input
================================================== */

input[type="file"] {
    width: 100%;
    padding: 0;

    overflow: hidden;

    background: var(--surface-soft);
    color: var(--text-muted);

    border: 1px solid var(--border);
    border-radius: 10px;

    cursor: pointer;
}

input[type="file"]::file-selector-button {
    padding: 0.85rem 1rem;
    margin-right: 1rem;

    background: var(--primary-soft);
    color: var(--primary);

    border: 0;
    border-right: 1px solid var(--border);

    font: inherit;
    font-weight: 600;

    cursor: pointer;

    transition: background-color 0.15s ease;
}

input[type="file"]::file-selector-button:hover {
    background: var(--primary-soft-hover);
}

input[type="file"]:focus-visible {
    outline: 3px solid rgba(37, 99, 235, 0.2);
    outline-offset: 2px;
}


/* ==================================================
   Messages
================================================== */

.message {
    margin-bottom: 1.5rem;
    padding: 0.85rem 1rem;

    border-radius: var(--radius-small);

    font-size: 0.9rem;
}

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

    border: 1px solid var(--danger-border);
}


/* ==================================================
   Login
================================================== */

.auth-heading {
    margin-bottom: 2rem;
    text-align: center;
}

.auth-heading h1 {
    margin: 0;

    font-size: 2rem;
    font-weight: 700;
}

.auth-form {
    display: flex;
    flex-direction: column;
    gap: 1.25rem;
}

.auth-form button {
    width: 100%;
    margin-top: 0.25rem;
}


/* ==================================================
   Home
================================================== */

.home-header {
    display: flex;
    align-items: center;
    justify-content: space-between;

    gap: 2rem;
    margin-bottom: 2.5rem;
}

.home-header h1 {
    margin: 0;

    font-size: 2rem;
    font-weight: 700;
}

.logout-button {
    flex-shrink: 0;

    padding: 0.65rem 1rem;

    background: var(--surface);
    color: var(--text-muted);

    border: 1px solid var(--border);
}

.logout-button:hover {
    background: var(--surface-soft);
    color: var(--text);
}

.subjects-section h2 {
    margin: 0 0 1rem;

    font-size: 1.25rem;
}

.subjects-grid {
    display: grid;
    gap: 1.25rem;
}

.subject-card {
    overflow: hidden;

    background: var(--surface);

    border: 1px solid var(--border);
    border-radius: var(--radius);

    box-shadow: var(--shadow);
}

.subject-card-header {
    padding: 1.25rem 1.5rem;

    border-bottom: 1px solid var(--border);
}

.subject-card-header h3 {
    margin: 0;

    font-size: 1.1rem;
    font-weight: 600;
}

.subject-acronym {
    display: inline-block;

    margin-top: 0.25rem;

    color: var(--text-muted);

    font-size: 0.8rem;
    font-weight: 700;

    letter-spacing: 0.06em;
    text-transform: uppercase;
}

.task-list {
    display: flex;
    flex-direction: column;
}

.task-link {
    display: flex;
    align-items: center;
    justify-content: space-between;

    padding: 1rem 1.5rem;

    color: var(--text);
    text-decoration: none;

    border-bottom: 1px solid var(--border);

    transition:
        background-color 0.15s ease,
        color 0.15s ease;
}

.task-link:last-child {
    border-bottom: 0;
}

.task-link:hover {
    background: var(--surface-soft);
    color: var(--primary);
}

.task-link:focus-visible {
    outline: 3px solid rgba(37, 99, 235, 0.2);
    outline-offset: -3px;
}

.empty-message {
    margin: 0;
    padding: 1.25rem 1.5rem;

    color: var(--text-muted);
}


/* ==================================================
   Task / Results headings
================================================== */

.task-heading,
.results-heading {
    margin-bottom: 2rem;
}

.task-heading h1,
.results-heading h1 {
    margin: 0.25rem 0 0.5rem;

    font-size: 1.8rem;
    font-weight: 700;
}

.task-subject {
    margin: 0;

    color: var(--primary);

    font-size: 0.8rem;
    font-weight: 700;

    letter-spacing: 0.06em;
    text-transform: uppercase;
}


/* ==================================================
   Task upload page
================================================== */

.upload-form {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.upload-form button {
    width: 100%;
}

.task-bottom-bar {
    display: grid;
    grid-template-columns: 1fr auto;
    align-items: center;

    width: 100%;

    margin-top: 1.5rem;
    padding-top: 1.25rem;

    border-top: 1px solid var(--border);
}


/* ==================================================
   Navigation links
================================================== */

.back-link {
    color: var(--text-muted);

    font-size: 0.9rem;
    text-decoration: none;

    transition: color 0.15s ease;
}

.back-link:hover {
    color: var(--primary);
}


/* ==================================================
   Attempt badges
================================================== */

.attempt-count,
.task-attempt-badge {
    padding: 0.45rem 0.9rem;

    background: var(--primary-soft);
    color: var(--primary);

    border: 1px solid var(--primary-border);
    border-radius: 999px;

    font-size: 0.85rem;
    font-weight: 700;

    white-space: nowrap;
}

.results-actions .attempt-count {
    margin-left: auto;
}

.task-attempt-badge {
    justify-self: end;
}


/* ==================================================
   Results table
================================================== */

.results-table-wrapper {
    overflow-x: auto;

    border: 1px solid var(--border);
    border-radius: var(--radius);
}

.results-table {
    width: 100%;

    border-collapse: collapse;
}

.results-table th,
.results-table td {
    padding: 0.9rem 1rem;

    text-align: left;
    vertical-align: middle;

    border-bottom: 1px solid var(--border);
}

.results-table th {
    background: var(--surface-soft);
    color: var(--text-muted);

    font-size: 0.8rem;
    font-weight: 700;

    letter-spacing: 0.03em;
}

.results-table tr:last-child td {
    border-bottom: 0;
}

.result-name {
    font-weight: 600;
}

.result-name code {
    display: inline-block;

    padding: 0.2rem 0.45rem;

    background: var(--surface-soft);
    color: var(--text);

    border: 1px solid var(--border);
    border-radius: 6px;

    font-family:
        ui-monospace,
        SFMono-Regular,
        Menlo,
        Monaco,
        Consolas,
        monospace;

    font-size: 0.9rem;
}

.result-value {
    font-family:
        ui-monospace,
        SFMono-Regular,
        Menlo,
        Monaco,
        Consolas,
        monospace;

    font-size: 0.9rem;

    white-space: nowrap;
}


/* ==================================================
   Validation status
================================================== */

.status {
    display: inline-flex;
    align-items: center;

    padding: 0.3rem 0.65rem;

    border-radius: 999px;

    font-size: 0.8rem;
    font-weight: 700;

    white-space: nowrap;
}

.status-correct {
    background: var(--success-background);
    color: var(--success);

    border: 1px solid var(--success-border);
}

.status-incorrect {
    background: var(--danger-background);
    color: var(--danger);

    border: 1px solid var(--danger-border);
}


/* ==================================================
   Results footer
================================================== */

.results-actions {
    display: flex;
    align-items: center;

    gap: 1.25rem;

    margin-top: 1.75rem;
}


/* ==================================================
   Responsive
================================================== */

@media (max-width: 600px) {
    .page-container {
        width: min(100% - 1rem, 960px);
        padding: 1rem 0;
    }

    .centered-page,
    .auth-page {
        min-height: calc(100vh - 2rem);
    }

    .auth-card,
    .task-card,
    .results-card {
        padding: 1.5rem;

        border-radius: var(--radius);
    }

    .home-header {
        align-items: flex-start;

        margin-bottom: 2rem;
    }

    .home-header h1 {
        font-size: 1.7rem;
    }

    .subject-card-header,
    .task-link,
    .empty-message {
        padding-left: 1rem;
        padding-right: 1rem;
    }

    .results-table th,
    .results-table td {
        padding: 0.75rem;
    }

    .results-actions {
        flex-direction: column;
        align-items: stretch;
    }

    .results-actions .button {
        width: 100%;
    }

    .results-actions .back-link {
        text-align: center;
    }

    .results-actions .attempt-count {
        align-self: flex-end;

        margin-left: 0;
    }

    .task-bottom-bar {
        grid-template-columns: 1fr;
        gap: 0.75rem;
    }

    .task-attempt-badge {
        justify-self: end;
    }
}