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

body {
    background-color: #f8f9fa;
    display: flex;
    justify-content: center;
    padding: 40px 20px;
}

.container {
    width: 100%;
    max-width: 500px;
}

.header {
    margin-bottom: 30px;
    text-align: center;
}

.back-btn {
    text-decoration: none;
    color: #6c757d;
    font-size: 0.9rem;
    transition: 0.3s;
    display: inline-block;
    margin-bottom: 10px;
}

.back-btn:hover {
    color: #007bff;
}

h1 {
    color: #333;
    font-size: 1.8rem;
}

/* Danh sách bài tập */
.exercise-grid {
    display: flex;
    flex-direction: column;
    gap: 15px;
}

.exercise-card {
    display: flex;
    align-items: center;
    background: white;
    text-decoration: none;
    color: #2d3436;
    padding: 20px;
    border-radius: 15px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.05);
    transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
    border: 1px solid transparent;
}

.exercise-card:hover {
    transform: translateY(-3px);
    box-shadow: 0 10px 20px rgba(0,0,0,0.1);
    border-color: #007bff;
    color: #007bff;
}

.icon {
    width: 40px;
    height: 40px;
    background: #eef2f7;
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    margin-right: 15px;
    color: #007bff;
}

.exercise-card span {
    font-size: 1.1rem;
    font-weight: 500;
}