* {
    box-sizing: border-box;
    font-family: system-ui, sans-serif;
}
body {
    margin: 0;
    padding: 20px;
    background-color: #f0f2f5;
}
.container {
    max-width: 800px;
    margin: 0 auto;
}
.card {
    background: white;
    border-radius: 8px;
    padding: 20px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    margin-bottom: 20px;
}
.input-group {
    display: flex;
    gap: 10px;
    margin-bottom: 20px;
}
input {
    padding: 8px 12px;
    border: 1px solid #ddd;
    border-radius: 4px;
    flex: 1;
}
button {
    padding: 8px 16px;
    border: none;
    border-radius: 4px;
    background-color: #0066cc;
    color: white;
    cursor: pointer;
    transition: background-color 0.2s;
}
button:hover {
    background-color: #0052a3;
}
button.secondary {
    background-color: #666;
}
button.success {
    background-color: #22c55e;
}
button.danger {
    background-color: #ef4444;
}
.vocab-list {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    gap: 15px;
}
.vocab-item {
    background: white;
    padding: 15px;
    border-radius: 8px;
    box-shadow: 0 1px 3px rgba(0,0,0,0.1);
}
.review-card {
    text-align: center;
    padding: 40px;
}
.word {
    font-size: 24px;
    margin-bottom: 20px;
}
.meaning {
    font-size: 20px;
    color: #666;
    margin-bottom: 20px;
}
.button-group {
    display: flex;
    gap: 10px;
    justify-content: center;
}
.progress {
    margin-top: 20px;
    font-size: 14px;
    color: #666;
}
.mode-toggle {
    text-align: center;
    margin-top: 20px;
}