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

body {
    font-family: 'Arial', 'Helvetica', sans-serif;
    background: #2c3e50;
    min-height: 100vh;
    padding: 0;
    margin: 0;
    color: #1a1a1a;
}

.app-wrapper {
    display: flex;
    min-height: 100vh;
    gap: 0;
    padding: 0;
}

.sidebar {
    width: 280px;
    background: #34495e;
    border-right: 3px solid #1a252f;
    padding: 0;
    position: sticky;
    top: 0;
    height: 100vh;
    overflow-y: auto;
    box-shadow: 2px 0 10px rgba(0, 0, 0, 0.3);
}

.sidebar-header {
    background: #1a252f;
    padding: 20px;
    border-bottom: 2px solid #0f1419;
}

.sidebar-header h2 {
    color: #ecf0f1;
    font-size: 1.2em;
    font-weight: bold;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.sidebar-item {
    padding: 15px 20px;
    cursor: pointer;
    transition: background-color 0.2s;
    border-bottom: 1px solid #2c3e50;
    background: #34495e;
    color: #ecf0f1;
}

.sidebar-item:hover {
    background: #3d566e;
}

.sidebar-item.active {
    background: #1a252f;
    border-left: 4px solid #3498db;
    color: #ecf0f1;
    font-weight: bold;
}

.sidebar-item.completed {
    background: #1e3a2e;
    border-left: 4px solid #27ae60;
}

.sidebar-item.completed:hover {
    background: #2a4a3a;
}

.sidebar-item.completed.active {
    background: #1a252f;
    border-left: 4px solid #27ae60;
}

.sidebar-item-title {
    font-size: 0.95em;
    line-height: 1.4;
}

.main-content {
    flex: 1;
    min-width: 0;
    background: #ecf0f1;
}

.container {
    max-width: 100%;
    background: #ffffff;
    padding: 0;
    box-shadow: 0 0 20px rgba(0, 0, 0, 0.1);
    min-height: 100vh;
}

header {
    background: #1a252f;
    padding: 25px 40px;
    border-bottom: 4px solid #3498db;
    color: #ecf0f1;
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: 1200px;
    margin: 0 auto;
}

h1 {
    font-size: 1.8em;
    color: #ecf0f1;
    margin: 0;
    font-weight: bold;
    text-transform: uppercase;
    letter-spacing: 2px;
}

.points-display {
    background: #2c3e50;
    padding: 15px 25px;
    border: 2px solid #3498db;
    border-radius: 4px;
    text-align: center;
}

.points-label {
    font-size: 0.85em;
    color: #bdc3c7;
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-bottom: 5px;
}

.points-value {
    font-size: 2em;
    font-weight: bold;
    color: #3498db;
}

.progress-section {
    background: #34495e;
    padding: 20px 40px;
    border-bottom: 2px solid #2c3e50;
}

.progress-content {
    max-width: 1200px;
    margin: 0 auto;
}

.progress-label {
    font-size: 0.9em;
    color: #ecf0f1;
    margin-bottom: 10px;
    font-weight: bold;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.progress-bar-container {
    width: 100%;
    height: 25px;
    background: #2c3e50;
    border: 1px solid #1a252f;
    overflow: hidden;
    margin-bottom: 8px;
}

.progress-bar {
    height: 100%;
    background: #3498db;
    width: 0%;
    transition: width 0.5s ease;
}

.progress-text {
    font-size: 0.9em;
    color: #bdc3c7;
    font-weight: bold;
}

.task-section {
    padding: 30px 40px;
    max-width: 1200px;
    margin: 0 auto;
}

.chapter-description {
    background: #f8f9fa;
    padding: 20px 25px;
    margin-bottom: 30px;
    font-size: 1em;
    line-height: 1.7;
    color: #2c3e50;
    border-left: 4px solid #3498db;
    border-top: 1px solid #e0e0e0;
    border-right: 1px solid #e0e0e0;
    border-bottom: 1px solid #e0e0e0;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
}

.task-container {
    display: grid;
    gap: 25px;
}

.task-card {
    background: #ffffff;
    padding: 30px;
    border: 2px solid #e0e0e0;
    border-left: 4px solid #3498db;
    transition: border-color 0.2s, box-shadow 0.2s;
    position: relative;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
}

.task-card:hover {
    border-color: #3498db;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

.task-card.confetti-animation {
    animation: confettiFadeOut 1.5s ease forwards;
}

@keyframes confettiFadeOut {
    0% {
        opacity: 1;
    }
    100% {
        opacity: 0;
        transform: translateY(-20px);
    }
}

.confetti {
    position: absolute;
    width: 8px;
    height: 8px;
    background: #3498db;
    animation: confettiFall linear forwards;
    z-index: 1000;
    pointer-events: none;
}

@keyframes confettiFall {
    0% {
        transform: translateY(0) translateX(0) rotate(0deg);
        opacity: 1;
    }
    100% {
        transform: translateY(400px) translateX(calc(var(--random-x, 0) * 100px)) rotate(720deg);
        opacity: 0;
    }
}

.task-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    padding-bottom: 15px;
    border-bottom: 2px solid #e0e0e0;
}

.task-title {
    font-size: 1.1em;
    font-weight: bold;
    color: #1a252f;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.task-points {
    background: #34495e;
    color: #ecf0f1;
    padding: 6px 15px;
    border-radius: 2px;
    font-weight: bold;
    font-size: 0.9em;
    border: 1px solid #2c3e50;
}

.task-question {
    font-size: 1.15em;
    margin: 25px 0;
    color: #2c3e50;
    line-height: 1.7;
    white-space: pre-line;
    font-weight: normal;
}

.task-input-group {
    display: flex;
    gap: 15px;
    align-items: center;
    justify-content: flex-start;
    margin: 25px 0 15px 0;
    padding-top: 20px;
    border-top: 1px solid #e0e0e0;
}

.task-input {
    font-size: 1.2em;
    padding: 12px 18px;
    border: 2px solid #bdc3c7;
    border-radius: 2px;
    width: 150px;
    text-align: center;
    font-family: 'Arial', sans-serif;
    font-weight: bold;
    background: #ffffff;
    color: #1a1a1a;
}

.task-input:focus {
    outline: none;
    border-color: #3498db;
    box-shadow: 0 0 0 3px rgba(52, 152, 219, 0.1);
}

.task-button {
    background: #3498db;
    color: white;
    border: none;
    padding: 12px 30px;
    font-size: 1em;
    border-radius: 2px;
    cursor: pointer;
    font-family: 'Arial', sans-serif;
    font-weight: bold;
    text-transform: uppercase;
    letter-spacing: 1px;
    transition: background-color 0.2s;
}

.task-button:hover {
    background: #2980b9;
}

.task-button:active {
    background: #21618c;
}

.task-button:disabled {
    background: #95a5a6;
    cursor: not-allowed;
}

.task-status {
    margin-top: 15px;
    font-size: 1em;
    font-weight: bold;
    min-height: 25px;
}

.task-status.success {
    color: #27ae60;
}

.task-status.error {
    color: #e74c3c;
}

.task-status.completed {
    color: #f39c12;
}

.message {
    position: fixed;
    top: 20px;
    right: 20px;
    padding: 15px 25px;
    border-radius: 2px;
    font-weight: bold;
    font-size: 1em;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
    transform: translateX(400px);
    transition: transform 0.3s ease;
    z-index: 1000;
    border: 2px solid;
}

.message.show {
    transform: translateX(0);
}

.message.success {
    background: #27ae60;
    color: white;
    border-color: #229954;
}

.message.error {
    background: #e74c3c;
    color: white;
    border-color: #c0392b;
}

@media (max-width: 900px) {
    .app-wrapper {
        flex-direction: column;
    }
    
    .sidebar {
        width: 100%;
        position: relative;
        height: auto;
        max-height: 300px;
        border-right: none;
        border-bottom: 3px solid #1a252f;
    }
    
    .sidebar-item {
        border-bottom: 1px solid #2c3e50;
    }
    
    .header-content {
        flex-direction: column;
        gap: 20px;
        align-items: flex-start;
    }
}

@media (max-width: 600px) {
    .container {
        padding: 0;
    }
    
    header {
        padding: 20px;
    }
    
    h1 {
        font-size: 1.4em;
    }
    
    .points-value {
        font-size: 1.5em;
    }
    
    .task-section {
        padding: 20px;
    }
    
    .task-input-group {
        flex-direction: column;
        align-items: stretch;
    }
    
    .task-input {
        width: 100%;
    }
    
    .task-button {
        width: 100%;
    }
    
    .sidebar-item {
        padding: 12px 15px;
    }
    
    .sidebar-item-title {
        font-size: 0.9em;
    }
}