:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --bg-color: #f8fafc;
    --card-bg: #ffffff;
    --text-color: #1e293b;
    --code-bg: #1e1e1e;
    --code-text: #d4d4d4;
    --border-color: #e2e8f0;
    --success-color: #22c55e;
    --error-color: #ef4444;
    --terminal-bg: #2d0a0a;
    /* Dark reddish tone like the screenshot */
    --terminal-text: #e5e5e5;
}

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

body {
    font-family: 'Inter', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
    padding: 2rem;
}

.container {
    max-width: 800px;
    margin: 0 auto;
}

header {
    text-align: center;
    margin-bottom: 3rem;
}

header h1 {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    color: var(--text-color);
}

.problem-card {
    background: var(--card-bg);
    border-radius: 12px;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    margin-bottom: 2rem;
    overflow: hidden;
    border: 1px solid var(--border-color);
}

.problem-header {
    padding: 1.5rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    gap: 1rem;
    background-color: #f1f5f9;
}

.badge {
    background-color: var(--primary-color);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: 9999px;
    font-size: 0.875rem;
    font-weight: 600;
}

.problem-header h2 {
    font-size: 1.25rem;
    font-weight: 600;
}

.problem-body {
    padding: 1.5rem;
}

.execution-result {
    margin: 1.5rem 0;
    border-radius: 6px;
    overflow: hidden;
    border: 1px solid #4a0f0f;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
}

.terminal-header {
    background-color: #8b0000;
    /* Dark red header like screenshot */
    color: white;
    padding: 0.25rem 0.75rem;
    font-size: 0.75rem;
    font-weight: bold;
}

.terminal-body {
    background-color: #fff;
    color: #000;
    padding: 1rem;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.9rem;
    border-left: 4px solid #8b0000;
}

.comment {
    color: #666;
    font-size: 0.85rem;
    margin-left: 1rem;
}

.code-block {
    background-color: var(--bg-color);
    padding: 1.5rem;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    overflow-x: auto;
}

pre {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.95rem;
    color: #333;
}

.code-select {
    font-family: 'JetBrains Mono', monospace;
    padding: 0.25rem 0.5rem;
    border-radius: 4px;
    border: 1px solid #cbd5e1;
    background-color: white;
    font-size: 0.95rem;
    cursor: pointer;
    transition: all 0.2s;
}

.code-select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.code-select.correct {
    border-color: var(--success-color);
    background-color: #f0fdf4;
}

.code-select.incorrect {
    border-color: var(--error-color);
    background-color: #fef2f2;
}

.code-input {
    font-family: 'JetBrains Mono', monospace;
    padding: 0.25rem 0.5rem;
    border-radius: 4px;
    border: 1px solid #cbd5e1;
    background-color: white;
    font-size: 0.95rem;
    transition: all 0.2s;
    width: 60px;
    text-align: center;
}

.code-input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.code-input.correct {
    border-color: var(--success-color);
    background-color: #f0fdf4;
}

.code-input.incorrect {
    border-color: var(--error-color);
    background-color: #fef2f2;
}

.code-input.wide {
    width: 120px;
}

.answer-hint {
    display: block;
    color: var(--error-color);
    font-size: 0.85rem;
    font-weight: 600;
    margin-top: 0.25rem;
    margin-left: 0.5rem;
}

.question-text {
    margin-top: 1.5rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--border-color);
}

.actions {
    text-align: center;
    margin-top: 2rem;
    margin-bottom: 4rem;
    display: flex;
    flex-direction: column;
    gap: 1rem;
    align-items: center;
}

.primary-btn {
    background-color: var(--primary-color);
    color: white;
    border: none;
    padding: 0.75rem 2rem;
    font-size: 1rem;
    font-weight: 600;
    border-radius: 8px;
    cursor: pointer;
    transition: background-color 0.2s;
}

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

.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 1000;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.3s;
}

.modal.visible {
    opacity: 1;
    pointer-events: auto;
}

.modal-content {
    background-color: white;
    padding: 2rem;
    border-radius: 12px;
    max-width: 400px;
    width: 90%;
    text-align: center;
    transform: translateY(20px);
    transition: transform 0.3s;
}

.modal.visible .modal-content {
    transform: translateY(0);
}

.modal h2 {
    margin-bottom: 1rem;
    color: var(--text-color);
}

.modal p {
    margin-bottom: 1.5rem;
    color: #475569;
}

.secondary-btn {
    background-color: #e2e8f0;
    color: var(--text-color);
    border: none;
    padding: 0.5rem 1.5rem;
    font-size: 0.9rem;
    font-weight: 600;
    border-radius: 6px;
    cursor: pointer;
    transition: background-color 0.2s;
}

.secondary-btn:hover {
    background-color: #cbd5e1;
}

.hidden {
    display: none;
}

.navigation {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
    padding: 1rem;
    background-color: var(--card-bg);
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.nav-btn {
    background-color: var(--primary-color);
    color: white;
    border: none;
    padding: 0.5rem 1.5rem;
    font-size: 0.9rem;
    font-weight: 600;
    border-radius: 6px;
    cursor: pointer;
    transition: background-color 0.2s;
}

.nav-btn:hover:not(:disabled) {
    background-color: var(--primary-hover);
}

.nav-btn:disabled {
    background-color: #cbd5e1;
    cursor: not-allowed;
    opacity: 0.6;
}

.problem-counter {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-color);
}