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

:root {
    --bg-dark: #0a0e17;
    --bg-card: #131a2b;
    --bg-panel: #1a2332;
    --text-primary: #e0e6ed;
    --text-secondary: #8892a0;
    --accent-green: #00ff88;
    --accent-green-dim: #00cc6a;
    --accent-blue: #4dabf7;
    --easy-color: #51cf66;
    --medium-color: #fcc419;
    --hard-color: #ff6b6b;
    --success: #00ff88;
    --error: #ff4757;
    --border: rgba(0, 255, 136, 0.15);
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #0a0e17 0%, #131a2b 50%, #0d1a2d 100%);
    color: var(--text-primary);
    min-height: 100vh;
}

/* Header */
.header {
    background: rgba(10, 14, 23, 0.95);
    backdrop-filter: blur(10px);
    padding: 15px 20px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: sticky;
    top: 0;
    z-index: 100;
    border-bottom: 1px solid var(--border);
}

.header h1 {
    font-size: 1.4rem;
    color: var(--accent-green);
    font-weight: 700;
}

.back-button {
    color: var(--accent-green);
    text-decoration: none;
    padding: 8px 16px;
    border: 1px solid var(--accent-green);
    border-radius: 20px;
    font-size: 0.85rem;
    transition: all 0.3s ease;
}

.back-button:hover {
    background: var(--accent-green);
    color: var(--bg-dark);
}

/* Container */
.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 30px 20px;
}

/* Intro Panel */
.intro-panel {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 20px 24px;
    margin-bottom: 24px;
    line-height: 1.6;
    color: var(--text-secondary);
}

/* Progress Section */
.progress-section {
    margin-bottom: 30px;
}

.progress-stats {
    display: flex;
    justify-content: space-between;
    margin-bottom: 8px;
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.progress-bar {
    height: 6px;
    background: var(--bg-panel);
    border-radius: 3px;
    overflow: hidden;
    margin-bottom: 10px;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--accent-green-dim), var(--accent-green));
    border-radius: 3px;
    transition: width 0.5s ease;
    width: 0%;
}

.reset-btn {
    background: none;
    border: 1px solid var(--text-secondary);
    color: var(--text-secondary);
    padding: 4px 12px;
    border-radius: 12px;
    font-size: 0.75rem;
    cursor: pointer;
    transition: all 0.3s ease;
}

.reset-btn:hover {
    border-color: var(--error);
    color: var(--error);
}

/* Challenge Grid */
.challenge-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 20px;
}

/* Challenge Card */
.challenge-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 24px;
    cursor: pointer;
    transition: all 0.3s ease;
    position: relative;
}

.challenge-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 8px 30px rgba(0, 255, 136, 0.1);
    border-color: var(--accent-green);
}

.challenge-card.solved {
    border-color: var(--accent-green-dim);
}

.challenge-card.solved::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    border-radius: 12px;
    background: rgba(0, 255, 136, 0.03);
    pointer-events: none;
}

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

.challenge-icon {
    font-size: 1.8rem;
}

.challenge-title {
    font-size: 1.15rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 8px;
}

.challenge-desc {
    font-size: 0.85rem;
    color: var(--text-secondary);
    line-height: 1.5;
    margin-bottom: 16px;
}

.challenge-card-footer {
    display: flex;
    align-items: center;
    gap: 8px;
    flex-wrap: wrap;
}

/* Badges */
.difficulty-badge {
    font-size: 0.7rem;
    font-weight: 700;
    padding: 3px 10px;
    border-radius: 10px;
    letter-spacing: 0.5px;
}

.difficulty-easy {
    background: rgba(81, 207, 102, 0.15);
    color: var(--easy-color);
}

.difficulty-medium {
    background: rgba(252, 196, 25, 0.15);
    color: var(--medium-color);
}

.difficulty-hard {
    background: rgba(255, 107, 107, 0.15);
    color: var(--hard-color);
}

.category-tag {
    font-size: 0.7rem;
    padding: 3px 10px;
    border-radius: 10px;
    background: rgba(77, 171, 247, 0.15);
    color: var(--accent-blue);
}

.points-tag {
    font-size: 0.7rem;
    padding: 3px 10px;
    border-radius: 10px;
    background: rgba(255, 255, 255, 0.06);
    color: var(--text-secondary);
}

.solved-badge {
    font-size: 0.7rem;
    padding: 3px 10px;
    border-radius: 10px;
    background: rgba(0, 255, 136, 0.15);
    color: var(--accent-green);
    font-weight: 600;
}

.points-possible {
    font-size: 0.7rem;
    padding: 3px 10px;
    border-radius: 10px;
    background: rgba(255, 255, 255, 0.06);
    color: var(--text-secondary);
}

/* Detail View */
.challenge-icon-lg {
    font-size: 2.5rem;
}

.detail-header {
    display: flex;
    align-items: center;
    gap: 20px;
    margin-bottom: 28px;
}

.detail-title-group h2 {
    font-size: 1.6rem;
    font-weight: 700;
    margin-bottom: 8px;
}

.detail-meta {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
    align-items: center;
}

/* Panels */
.briefing-panel,
.data-panel,
.flag-section,
.hints-section,
.solution-panel,
.tool-panel {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 20px 24px;
    margin-bottom: 20px;
}

.panel-label {
    font-size: 0.7rem;
    font-weight: 700;
    letter-spacing: 1.5px;
    color: var(--accent-green);
    margin-bottom: 12px;
    text-transform: uppercase;
}

.briefing-panel p {
    color: var(--text-secondary);
    line-height: 1.7;
    font-size: 0.95rem;
}

/* Data Panel */
.data-content {
    background: var(--bg-dark);
    border: 1px solid rgba(255, 255, 255, 0.06);
    border-radius: 8px;
    padding: 16px;
    display: flex;
    align-items: flex-start;
    gap: 12px;
}

.data-content code {
    flex: 1;
    font-family: 'Cascadia Code', 'Consolas', 'Courier New', monospace;
    font-size: 0.9rem;
    color: var(--accent-green);
    word-break: break-all;
    line-height: 1.6;
}

.copy-btn {
    background: rgba(0, 255, 136, 0.1);
    color: var(--accent-green);
    border: 1px solid var(--accent-green);
    padding: 4px 12px;
    border-radius: 6px;
    font-size: 0.75rem;
    cursor: pointer;
    white-space: nowrap;
    transition: all 0.3s ease;
}

.copy-btn:hover {
    background: var(--accent-green);
    color: var(--bg-dark);
}

.data-extra {
    margin-top: 12px;
    font-family: 'Cascadia Code', 'Consolas', 'Courier New', monospace;
    font-size: 0.85rem;
    color: var(--text-secondary);
    line-height: 1.6;
    white-space: pre-wrap;
}

/* Flag Section */
.flag-row {
    display: flex;
    gap: 10px;
}

.flag-input {
    flex: 1;
    background: var(--bg-dark);
    border: 2px solid rgba(255, 255, 255, 0.1);
    border-radius: 8px;
    padding: 12px 16px;
    color: var(--text-primary);
    font-family: 'Cascadia Code', 'Consolas', 'Courier New', monospace;
    font-size: 0.95rem;
    outline: none;
    transition: border-color 0.3s ease;
}

.flag-input:focus {
    border-color: var(--accent-green);
}

.flag-input.input-success {
    border-color: var(--success);
    box-shadow: 0 0 15px rgba(0, 255, 136, 0.2);
}

.flag-btn {
    background: linear-gradient(135deg, var(--accent-green-dim), var(--accent-green));
    color: var(--bg-dark);
    border: none;
    padding: 12px 24px;
    border-radius: 8px;
    font-weight: 700;
    font-size: 0.9rem;
    cursor: pointer;
    transition: all 0.3s ease;
}

.flag-btn:hover {
    transform: scale(1.03);
    box-shadow: 0 4px 15px rgba(0, 255, 136, 0.3);
}

.flag-feedback {
    margin-top: 10px;
    font-size: 0.9rem;
    font-weight: 600;
    min-height: 24px;
}

.flag-feedback.success {
    color: var(--success);
}

.flag-feedback.error {
    color: var(--error);
}

.solved-section {
    border-color: var(--accent-green-dim);
}

.solved-message {
    color: var(--accent-green);
    font-weight: 600;
}

/* Hints */
.hints-grid {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.hint-card {
    background: var(--bg-dark);
    border: 1px solid rgba(255, 255, 255, 0.06);
    border-radius: 8px;
    padding: 14px 18px;
}

.hint-card.revealed {
    border-color: var(--medium-color);
}

.hint-card.revealed .hint-header {
    color: var(--medium-color);
}

.hint-card.locked {
    opacity: 0.6;
}

.hint-header {
    font-size: 0.8rem;
    font-weight: 700;
    margin-bottom: 6px;
    color: var(--text-secondary);
}

.hint-cost {
    font-weight: 400;
    opacity: 0.7;
}

.hint-card p {
    color: var(--text-secondary);
    font-size: 0.9rem;
    line-height: 1.5;
}

.hint-btn {
    background: rgba(252, 196, 25, 0.1);
    color: var(--medium-color);
    border: 1px solid rgba(252, 196, 25, 0.3);
    padding: 10px 18px;
    border-radius: 8px;
    cursor: pointer;
    font-size: 0.85rem;
    width: 100%;
    transition: all 0.3s ease;
}

.hint-btn:hover {
    background: rgba(252, 196, 25, 0.2);
    border-color: var(--medium-color);
}

/* Solution Panel */
.solution-panel {
    border-color: rgba(0, 255, 136, 0.3);
}

.solution-panel p {
    color: var(--text-secondary);
    line-height: 1.7;
    font-size: 0.9rem;
}

/* Tool Panel (Hash Tester) */
.tool-desc {
    color: var(--text-secondary);
    font-size: 0.85rem;
    margin-bottom: 12px;
}

.tool-row {
    display: flex;
    gap: 10px;
    margin-bottom: 10px;
}

.tool-input {
    flex: 1;
    background: var(--bg-dark);
    border: 2px solid rgba(255, 255, 255, 0.1);
    border-radius: 8px;
    padding: 10px 14px;
    color: var(--text-primary);
    font-family: 'Cascadia Code', 'Consolas', 'Courier New', monospace;
    font-size: 0.85rem;
    outline: none;
    transition: border-color 0.3s ease;
}

.tool-input:focus {
    border-color: var(--accent-blue);
}

.tool-btn {
    background: rgba(77, 171, 247, 0.15);
    color: var(--accent-blue);
    border: 1px solid var(--accent-blue);
    padding: 10px 18px;
    border-radius: 8px;
    cursor: pointer;
    font-size: 0.85rem;
    font-weight: 600;
    transition: all 0.3s ease;
}

.tool-btn:hover {
    background: var(--accent-blue);
    color: var(--bg-dark);
}

.hash-result {
    font-family: 'Cascadia Code', 'Consolas', 'Courier New', monospace;
    font-size: 0.8rem;
    color: var(--accent-green);
    word-break: break-all;
    min-height: 20px;
}

/* Completion Overlay */
.completion-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.8);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 200;
}

.completion-modal {
    background: var(--bg-card);
    border: 2px solid var(--accent-green);
    border-radius: 16px;
    padding: 40px;
    max-width: 450px;
    text-align: center;
}

.completion-modal h2 {
    font-size: 1.6rem;
    color: var(--accent-green);
    margin-bottom: 12px;
}

.completion-score {
    font-size: 1.3rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 12px;
}

.completion-modal p {
    color: var(--text-secondary);
    margin-bottom: 20px;
    line-height: 1.5;
}

.completion-close {
    background: linear-gradient(135deg, var(--accent-green-dim), var(--accent-green));
    color: var(--bg-dark);
    border: none;
    padding: 12px 32px;
    border-radius: 8px;
    font-weight: 700;
    font-size: 0.95rem;
    cursor: pointer;
    transition: all 0.3s ease;
}

.completion-close:hover {
    transform: scale(1.05);
}

/* Animations */
@keyframes shake {
    0%, 100% { transform: translateX(0); }
    20% { transform: translateX(-8px); }
    40% { transform: translateX(8px); }
    60% { transform: translateX(-6px); }
    80% { transform: translateX(6px); }
}

.input-shake {
    animation: shake 0.5s ease;
}

/* Responsive */
@media (max-width: 768px) {
    .header h1 {
        font-size: 1.1rem;
    }

    .back-button {
        font-size: 0.75rem;
        padding: 6px 12px;
    }

    .container {
        padding: 20px 14px;
    }

    .challenge-grid {
        grid-template-columns: 1fr;
    }

    .detail-header {
        flex-direction: column;
        align-items: flex-start;
        gap: 12px;
    }

    .flag-row,
    .tool-row {
        flex-direction: column;
    }

    .flag-btn,
    .tool-btn {
        width: 100%;
    }

    .data-content {
        flex-direction: column;
    }

    .copy-btn {
        align-self: flex-end;
    }

    .completion-modal {
        margin: 20px;
        padding: 28px;
    }
}