:root {
    --primary-color: #4a6bff;
    --secondary-color: #f5f7ff;
    --text-color: #333;
    --light-text: #777;
    --border-color: #e0e0e0;
    --success-color: #28a745;
    --warning-color: #ffc107;
    --danger-color: #dc3545;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Poppins', sans-serif;
}

body {
    background-color: #f9fafb;
    color: var(--text-color);
    line-height: 1.6;
}

.screen {
    display: none;
}

.screen.active {
    display: block;
}

/* Login Screen Styles */
.login-container {
    max-width: 400px;
    margin: 5rem auto;
    padding: 2rem;
    background: white;
    border-radius: 10px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
    text-align: center;
}

.login-container h1 {
    margin-bottom: 2rem;
    color: var(--primary-color);
}

.form-group {
    margin-bottom: 1.5rem;
    text-align: left;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
}

.form-group input {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: 5px;
    font-size: 1rem;
}

.form-group input:focus {
    outline: none;
    border-color: var(--primary-color);
}

.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: 5px;
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.3s ease;
}

.btn:hover {
    background-color: #3a5bef;
    transform: translateY(-2px);
}

.btn-outline {
    background-color: transparent;
    border: 1px solid var(--primary-color);
    color: var(--primary-color);
}

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

.btn-sm {
    padding: 0.5rem 1rem;
    font-size: 0.9rem;
}

.footer {
    margin-top: 1.5rem;
    font-size: 0.9rem;
    color: var(--light-text);
}

.footer a {
    color: var(--primary-color);
    text-decoration: none;
}

/* Dashboard Styles */
header {
    background-color: white;
    padding: 1rem 2rem;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
}

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

main {
    display: flex;
    max-width: 1200px;
    margin: 2rem auto;
    gap: 2rem;
}

.sidebar {
    width: 250px;
    background-color: white;
    border-radius: 10px;
    padding: 1.5rem;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.05);
    height: fit-content;
}

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

.avatar {
    width: 80px;
    height: 80px;
    background-color: var(--primary-color);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    font-weight: bold;
    margin: 0 auto 1rem;
}

.sidebar h3 {
    font-size: 1.2rem;
    margin-bottom: 0.25rem;
}

.sidebar p {
    color: var(--light-text);
    font-size: 0.9rem;
}

nav ul {
    list-style: none;
}

nav li {
    margin-bottom: 0.5rem;
}

nav li a {
    display: block;
    padding: 0.75rem 1rem;
    color: var(--text-color);
    text-decoration: none;
    border-radius: 5px;
    transition: all 0.3s ease;
}

nav li a:hover {
    background-color: var(--secondary-color);
}

nav li.active a {
    background-color: var(--primary-color);
    color: white;
}

.content {
    flex: 1;
}

.content-section {
    display: none;
    background-color: white;
    border-radius: 10px;
    padding: 2rem;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.05);
}

.content-section.active {
    display: block;
}

.cards-container {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    gap: 1.5rem;
    margin-top: 1.5rem;
}

.card {
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 1.5rem;
    transition: all 0.3s ease;
}

.card:hover {
    transform: translateY(-5px);
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
}

.card h3 {
    margin-bottom: 0.5rem;
}

.card p {
    color: var(--light-text);
    font-size: 0.9rem;
    margin-bottom: 1rem;
}

.exercises-container {
    margin-top: 1.5rem;
}

.exercise {
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 1.5rem;
    margin-bottom: 1rem;
}

.exercise-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 0.5rem;
}

.due-date {
    font-size: 0.85rem;
    color: var(--light-text);
}

.exercise-actions {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 1rem;
}

.status {
    font-size: 0.85rem;
    padding: 0.25rem 0.5rem;
    border-radius: 4px;
    font-weight: 500;
}

.status.pending {
    background-color: rgba(255, 193, 7, 0.1);
    color: var(--warning-color);
}

.status.completed {
    background-color: rgba(40, 167, 69, 0.1);
    color: var(--success-color);
}

.status.not-started {
    background-color: rgba(220, 53, 69, 0.1);
    color: var(--danger-color);
}

.progress-container {
    margin-top: 1.5rem;
}

.progress-chart {
    margin-bottom: 2rem;
}

.progress-stats {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: 1.5rem;
}

.stat-card {
    background-color: var(--secondary-color);
    padding: 1.5rem;
    border-radius: 8px;
    text-align: center;
}

.stat-card h3 {
    font-size: 1rem;
    margin-bottom: 0.5rem;
    color: var(--light-text);
}

.stat-value {
    font-size: 2rem;
    font-weight: 600;
    color: var(--primary-color);
}

/* Responsive Styles */
@media (max-width: 768px) {
    main {
        flex-direction: column;
    }
    
    .sidebar {
        width: 100%;
    }
    
    .cards-container {
        grid-template-columns: 1fr;
    }
}