body {
    font-family: 'Comic Sans MS', cursive;
    background: linear-gradient(135deg, #FFD700, #FFA07A);
    margin: 0;
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
}

.container {
    background-color: white;
    border-radius: 20px;
    padding: 2rem;
    box-shadow: 0 0 20px rgba(0,0,0,0.2);
    text-align: center;
}

h1 {
    color: #FF6B6B;
    margin-bottom: 2rem;
}

.game-container {
    display: flex;
    flex-direction: column;
    gap: 4rem;
    margin: 2rem 0;
    align-items: center;
    position: relative;
    min-height: 300px;
}

.operations, .results {
    display: flex;
    flex-direction: row;
    gap: 1rem;
    flex-wrap: wrap;
    justify-content: center;
}

.operation, .result {
    padding: 1rem 2rem;
    min-width: 120px;
    background-color: #F8F9FA;
    border-radius: 10px;
    cursor: pointer;
    transition: all 0.3s ease;
    user-select: none;
    opacity: 0;
    font-size: 1.2rem;
}

.operation {
    border: 3px solid #4ECDC4;
}

.result {
    border: 3px solid #FF6B6B;
}

.selected {
    transform: scale(1.1);
    box-shadow: 0 0 10px rgba(0,0,0,0.2);
}

.correct {
    background-color: #98FB98;
}

.score {
    font-size: 1.5rem;
    color: #444;
    margin: 1rem 0;
}

.new-game-btn {
    background-color: #4ECDC4;
    color: white;
    border: none;
    padding: 1rem 2rem;
    border-radius: 10px;
    font-size: 1.2rem;
    cursor: pointer;
    transition: all 0.3s ease;
}

.new-game-btn:hover {
    background-color: #45b7b0;
    transform: scale(1.05);
}

.fade-out {
    opacity: 0;
    transform: scale(0.8);
    transition: all 0.5s ease;
}

.final-grade {
    font-size: 3rem;
    color: #FF6B6B;
    font-weight: bold;
    animation: popIn 0.5s ease-out;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    text-shadow: 2px 2px 4px rgba(0,0,0,0.2);
}

.operation-choice {
    margin-bottom: 2rem;
    display: flex;
    gap: 1rem;
    justify-content: center;
}

.operation-btn {
    background-color: #F8F9FA;
    border: 3px solid #4ECDC4;
    color: #444;
    padding: 0.8rem 1.5rem;
    border-radius: 10px;
    font-size: 1.2rem;
    cursor: pointer;
    transition: all 0.3s ease;
}

.operation-btn.selected {
    background-color: #4ECDC4;
    color: white;
}

.operation-btn:hover {
    transform: scale(1.05);
}

.difficulty-choice {
    margin-bottom: 1rem;
    display: flex;
    gap: 1rem;
    justify-content: center;
}

.difficulty-btn {
    background-color: #F8F9FA;
    border: 3px solid #FF6B6B;
    color: #444;
    padding: 0.8rem 1.5rem;
    border-radius: 10px;
    font-size: 1.2rem;
    cursor: pointer;
    transition: all 0.3s ease;
}

.difficulty-btn.selected {
    background-color: #FF6B6B;
    color: white;
}

.difficulty-btn:hover {
    transform: scale(1.05);
}

.carry-choice {
    margin-bottom: 2rem;
    display: flex;
    gap: 1rem;
    justify-content: center;
}

.carry-btn {
    background-color: #F8F9FA;
    border: 3px solid #4ECDC4;
    color: #444;
    padding: 0.8rem 1.5rem;
    border-radius: 10px;
    font-size: 1.2rem;
    cursor: pointer;
    transition: all 0.3s ease;
}

.carry-btn.selected {
    background-color: #4ECDC4;
    color: white;
}

.carry-btn:hover {
    transform: scale(1.05);
}

@keyframes popIn {
    0% {
        opacity: 0;
        transform: translate(-50%, -50%) scale(0.5);
    }
    70% {
        transform: translate(-50%, -50%) scale(1.2);
    }
    100% {
        opacity: 1;
        transform: translate(-50%, -50%) scale(1);
    }
}