:root {
    --bg-dark: #0a0a0f;
    --bg-card: #12121a;
    --bg-input: #1a1a24;
    --border: #2a2a3a;
    --border-focus: #3b82f6;

    --text-primary: #f0f0f5;
    --text-secondary: #8b8b9e;
    --text-muted: #5a5a6e;

    --accent-blue: #3b82f6;
    --accent-orange: #f59e0b;
    --accent-green: #10b981;
    --accent-purple: #8b5cf6;

    --font-sans: 'Inter', -apple-system, sans-serif;
    --font-mono: 'JetBrains Mono', monospace;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    background: var(--bg-dark);
    font-family: var(--font-sans);
    color: var(--text-primary);
    min-height: 100vh;
    line-height: 1.6;
}

div#enviar-input {
    margin-top: .5em;
}

.lista-alfabetica {
    list-style: none;
    padding-left: 1em;
}

div.enunciado {
    margin-top: 2em;
}

.enunciado>svg,
.enunciado>p>svg,
.enunciado>div>svg {
    display: block;
    margin: 0 auto;
}

.enunciado svg text {
    fill: var(--text-primary);
}

.enunciado svg line[stroke="black"] {
    stroke: var(--text-primary);
}

.enunciado table {
    border-collapse: collapse;
    margin: 1.5em auto;
    width: auto;
}

.enunciado th,
.enunciado td {
    border: 1px solid var(--border);
    padding: 0.6em 1.2em;
    text-align: center;
}

.enunciado th {
    background-color: var(--bg-input);
    font-weight: 600;
    color: var(--text-secondary);
}

.enunciado img {
    width: 350px;
    /* per evitar que si estam al mòbil faci el text més petit */
    display: block;
    margin: 0 auto;
    border-radius: 10px;
    margin-top: 2em;
}


/* Solo SVGs de diagramas, no los SVGs internos de KaTeX */

.exercici>svg,
.enunciado>svg,
.enunciado>p>svg,
.enunciado>div>svg {
    width: 100%;
    max-width: 500px;
    height: auto;
    margin-bottom: 1.5em;
}

/* és el p on està l'enunciat */
.enunciado p {
    margin-bottom: 2em;
}

/* Header */
.header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 16px 32px;
    border-bottom: 1px solid var(--border);
    position: sticky;
    top: 0;
    background: var(--bg-dark);
    z-index: 100;
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-weight: 600;
    font-size: 18px;
}

.logo-icon {
    width: 32px;
    height: 32px;
    background: var(--accent-blue);
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 16px;
}

.btn-icon {
    width: 40px;
    height: 40px;
    border-radius: 10px;
    border: 1px solid var(--border);
    background: transparent;
    color: var(--text-secondary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s;
}

.btn-icon:hover {
    border-color: var(--text-secondary);
    color: var(--text-primary);
}

/* Main layout */
.main {
    max-width: 800px;
    margin: 0 auto;
    padding: 40px 24px;
}

/* Breadcrumb */
.breadcrumb {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 14px;
    margin-bottom: 32px;
}

.breadcrumb a {
    color: var(--accent-blue);
    text-decoration: none;
    transition: opacity 0.2s;
}

.breadcrumb a:hover {
    opacity: 0.8;
}

.breadcrumb span {
    color: var(--text-muted);
}

.breadcrumb .current {
    color: var(--text-secondary);
}

/* Sección del tema */
.topic-header {
    text-align: center;
    margin-bottom: 40px;
}

.topic-tag {
    display: inline-block;
    padding: 6px 14px;
    background: rgba(139, 92, 246, 0.15);
    border: 1px solid rgba(139, 92, 246, 0.3);
    border-radius: 20px;
    font-size: 12px;
    font-weight: 500;
    color: var(--accent-purple);
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-bottom: 16px;
}

.topic-title {
    font-size: 24px;
    font-weight: 600;
    margin-bottom: 8px;
    line-height: 1.3;
}

/* Navegación de ejercicios */
.exercise-nav {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 20px;
    margin-bottom: 24px;
}

.nav-arrow {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    border: 1px solid var(--border);
    background: transparent;
    color: var(--text-secondary);
    cursor: pointer;
    display: flex !important;
    /* Sobrescribe d-block de Bootstrap */
    align-items: center;
    justify-content: center;
    transition: all 0.2s;
    font-size: 18px;
    line-height: 1;
}

.nav-arrow:hover {
    border-color: var(--accent-blue);
    color: var(--accent-blue);
    background: rgba(59, 130, 246, 0.1);
}

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

.exercise-number {
    font-family: var(--font-sans);
    /*var(--font-mono);*/
    font-size: 16px;
    font-weight: 500;
}

.difficulty {
    display: flex;
    gap: 4px;
}

.difficulty-star {
    font-size: 14px;
    color: var(--text-muted);
}

.difficulty-star.active {
    color: var(--accent-orange);
}

/* Tarjeta del ejercicio */
.exercise-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 20px;
    padding: 36px;
    margin-bottom: 24px;
}

.exercise-label {
    font-size: 11px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 1.5px;
    color: var(--text-muted);
    margin-bottom: 16px;
}

.exercise-statement {
    font-size: 17px;
    line-height: 1.75;
    color: var(--text-primary);
}

.exercise-statement .num {
    font-family: var(--font-mono);
    font-weight: 500;
    color: var(--accent-orange);
    background: rgba(245, 158, 11, 0.1);
    padding: 2px 8px;
    border-radius: 6px;
    margin: 0 2px;
}

/* Input de respuesta */
.answer-section {
    background: transparent;
    /*border: 1px solid var(--border);*/
    border-radius: 20px;
    padding-top: 10px;
    padding-right: 28px;
    padding-left: 28px;
}

.answer-label {
    font-size: 11px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 1.5px;
    color: var(--text-muted);
    margin-bottom: 16px;
    display: flex;
    align-items: center;
    gap: 8px;
}

.answer-input2 {
    width: 100%;
    background: var(--bg-input);
    border: 2px solid var(--border);
    border-radius: 12px;
    padding: 16px 20px;
    font-family: var(--font-mono);
    font-size: 16px;
    color: var(--text-primary);
    resize: none;
    min-height: 100px;
    transition: border-color 0.2s;
}

.answer-input2::placeholder {
    color: var(--text-muted);
}

.answer-input2:focus {
    outline: none;
    border-color: var(--accent-blue);
}



/* entrada de text */
/* Área de input de respuesta */
.answer-input {
    width: 100%;
    background: #0a0a0f;
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 16px 20px;
    font-family: var(--font-mono);
    font-size: 16px;
    color: var(--text-primary);
    resize: none;
    min-height: 100px;
    transition: border-color 0.2s, box-shadow 0.2s;
}

.answer-input::placeholder {
    color: #5a5a6e;
}

/* Focus suavizado */
.answer-input:focus {
    outline: none;
    border-color: #5a5a6e;
    box-shadow: 0 0 0 2px rgba(59, 130, 246, 0.1);
}

.divider {
    margin-top: 2em;
    height: 1px;
    background: var(--border);
}



.answer-actions {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-top: 20px;
}

.action-buttons-left {
    display: flex;
    gap: 12px;
}

.btn-secondary {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 10px 16px;
    background: transparent;
    border: 1px solid var(--border);
    border-radius: 10px;
    color: var(--text-secondary);
    font-family: var(--font-sans);
    font-size: 14px;
    cursor: pointer;
    transition: all 0.2s;
}

.btn-secondary:hover {
    border-color: var(--text-secondary);
    color: var(--text-primary);
}

.btn-secondary svg {
    width: 18px;
    height: 18px;
}

.action-buttons-right {
    display: flex;
    gap: 12px;
}

.btn-hint {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 10px 18px;
    background: rgba(245, 158, 11, 0.1);
    border: 1px solid rgba(245, 158, 11, 0.3);
    border-radius: 10px;
    color: var(--accent-orange);
    font-family: var(--font-sans);
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
}

.btn-hint:hover {
    background: rgba(245, 158, 11, 0.2);
}

.btn-submit {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 12px 24px;
    background: var(--accent-blue);
    border: none;
    border-radius: 10px;
    color: white;
    font-family: var(--font-sans);
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
}

.btn-submit:hover {
    background: #2563eb;
    transform: translateY(-1px);
}

/* Progress indicator */
.progress-section {
    margin-top: 40px;
    padding-top: 32px;
    border-top: 1px solid var(--border);
}

.progress-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 12px;
}

.progress-label {
    font-size: 13px;
    color: var(--text-secondary);
}

.progress-count {
    font-family: var(--font-mono);
    font-size: 13px;
    color: var(--text-muted);
}

.progress-bar {
    height: 6px;
    background: var(--border);
    border-radius: 3px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    width: 35%;
    background: linear-gradient(90deg, var(--accent-blue), var(--accent-purple));
    border-radius: 3px;
    transition: width 0.5s ease;
}

/* Keyboard shortcuts hint */
.shortcuts {
    display: flex;
    justify-content: center;
    gap: 24px;
    margin-top: 32px;
}

.shortcut {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 12px;
    color: var(--text-muted);
}

.key {
    font-family: var(--font-mono);
    font-size: 11px;
    padding: 4px 8px;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 6px;
}

/* Notes section */
.notes {
    max-width: 800px;
    margin: 80px auto 0;
    padding: 32px;
    background: rgba(59, 130, 246, 0.05);
    border: 1px solid rgba(59, 130, 246, 0.2);
    border-radius: 16px;
}

.notes h3 {
    font-size: 16px;
    color: var(--accent-blue);
    margin-bottom: 20px;
    display: flex;
    align-items: center;
    gap: 8px;
}

.notes-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 32px;
}

.notes-column h4 {
    font-size: 13px;
    text-transform: uppercase;
    letter-spacing: 1px;
    color: var(--text-secondary);
    margin-bottom: 12px;
}

.notes ul {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.notes li {
    font-size: 14px;
    color: var(--text-secondary);
    padding-left: 20px;
    position: relative;
    line-height: 1.5;
}

.notes li::before {
    content: '→';
    position: absolute;
    left: 0;
    color: var(--accent-blue);
}

@media (max-width: 640px) {
    .notes-grid {
        grid-template-columns: 1fr;
    }

    .main {
        padding: 24px 16px;
    }

    .exercise-card,
    .answer-section {
        padding: 24px;
    }

    .answer-actions {
        flex-direction: column;
        gap: 16px;
    }

    .action-buttons-left,
    .action-buttons-right {
        width: 100%;
        justify-content: center;
    }
}