body {
    font-family: Arial, sans-serif;
    background-color: #f0f0f0;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
}

.container {
    text-align: center;
    padding: 20px;
    width: 90%;
    max-width: 800px;
}

h1, h2 {
    color: #333;
}

#setManagement, #cardManagement, #studyMode {
    margin: 20px 0;
    background: #fff;
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}

input, textarea, select, button {
    padding: 10px;
    margin: 5px;
    font-size: 16px;
    border: 1px solid #ccc;
    border-radius: 5px;
}

input, textarea {
    width: calc(100% - 30px);
    box-sizing: border-box;
}

textarea {
    height: 80px;
    resize: vertical;
}

select {
    width: 200px;
}

button {
    background-color: #007BFF;
    color: white;
    border: none;
    cursor: pointer;
}

button:hover {
    background-color: #0056b3;
}

button:disabled {
    background-color: #ccc;
    cursor: not-allowed;
}

#cardList {
    list-style: none;
    padding: 0;
    text-align: left;
}

#cardList li {
    padding: 10px;
    border-bottom: 1px solid #ddd;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

#cardList li button {
    background-color: #dc3545;
    padding: 5px 10px;
}

#cardList li button.edit {
    background-color: #ffc107;
    color: #333;
}

.flashcard {
    width: 400px;
    height: 300px;
    margin: 20px auto;
    perspective: 1000px;
}

.card-inner {
    position: relative;
    width: 100%;
    height: 100%;
    transition: transform 0.6s;
    transform-style: preserve-3d;
    cursor: pointer;
}

.flashcard.flipped .card-inner {
    transform: rotateY(180deg);
}

.card-front, .card-back {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    background-color: #fff;
    border: 2px solid #333;
    border-radius: 10px;
    padding: 20px;
    box-sizing: border-box;
    display: flex;
    flex-direction: column;
    justify-content: center;
}

.card-back {
    transform: rotateY(180deg);
    text-align: left;
}

.card-front h2 {
    margin: 0;
    color: #333;
}

.card-back p {
    margin: 10px 0;
    color: #555;
}

.navigation {
    margin-top: 20px;
}

#filterSelector {
    margin: 10px 0;
}

#starBtn {
    background-color: #ffc107;
    font-size: 20px;
    padding: 5px 15px;
}

#starBtn.starred {
    background-color: #ffca2c;
    color: #333;
}