* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Arial', sans-serif;
    background: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
    overflow-x: hidden;
}

.container {
    background: white;
    border-radius: 20px;
    padding: 40px;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
    max-width: 900px;
    width: 100%;
    position: relative;
}

h1 {
    color: #333;
    text-align: center;
    margin-bottom: 15px;
    font-size: 28px;
}

.instructions {
    text-align: center;
    color: #666;
    margin-bottom: 30px;
    font-size: 16px;
    line-height: 1.6;
}

.number-line-container {
    position: relative;
    margin: 40px 0;
}

.number-line {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 10px;
    position: relative;
    z-index: 2;
}

.timeline {
    position: absolute;
    top: 50%;
    left: 0;
    right: 0;
    height: 4px;
    background: #ddd;
    transform: translateY(-50%);
    z-index: 1;
}

.number-item {
    flex: 1;
    min-width: 60px;
    text-align: center;
    position: relative;
}

.number-item.filled {
    background: #4facfe;
    color: white;
    padding: 15px 10px;
    border-radius: 10px;
    font-size: 20px;
    font-weight: bold;
    box-shadow: 0 4px 10px rgba(79, 172, 254, 0.3);
}

.number-input {
    width: 100%;
    padding: 15px 5px;
    font-size: 18px;
    font-weight: bold;
    text-align: center;
    border: 3px solid #ddd;
    border-radius: 10px;
    background: white;
    transition: all 0.3s ease;
}

.number-input:focus {
    outline: none;
    border-color: #4facfe;
    box-shadow: 0 0 10px rgba(79, 172, 254, 0.3);
}

.number-input.correct {
    background: #4caf50;
    color: white;
    border-color: #45a049;
    animation: correct 0.5s ease;
}

.number-input.incorrect {
    background: #f44336;
    color: white;
    border-color: #da190b;
    animation: shake 0.5s ease;
}

.number-input.revealed {
    background: #ff9800;
    color: white;
    border-color: #f57c00;
}

.number-input:disabled {
    cursor: not-allowed;
}

@keyframes correct {
    0%, 100% { transform: scale(1); }
    50% { transform: scale(1.1); }
}

@keyframes shake {
    0%, 100% { transform: translateX(0); }
    25% { transform: translateX(-5px); }
    75% { transform: translateX(5px); }
}

.button-container {
    display: flex;
    gap: 15px;
    justify-content: center;
    margin: 30px 0 20px 0;
}

button {
    background: #4facfe;
    color: white;
    border: none;
    padding: 15px 30px;
    border-radius: 10px;
    font-size: 16px;
    font-weight: bold;
    cursor: pointer;
    transition: all 0.3s ease;
}

button:hover {
    background: #3d96e8;
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(79, 172, 254, 0.4);
}

button:active {
    transform: translateY(0);
}

.feedback {
    text-align: center;
    font-size: 18px;
    font-weight: bold;
    min-height: 30px;
    margin-top: 20px;
}

.feedback.success {
    color: #4caf50;
}

.feedback.error {
    color: #f44336;
}

.feedback.warning {
    color: #ff9800;
}

.info-box {
    background: #e3f2fd;
    border-left: 4px solid #2196f3;
    padding: 15px;
    border-radius: 5px;
    margin-top: 20px;
}

.info-box h3 {
    color: #1976d2;
    margin-bottom: 10px;
    font-size: 18px;
}

.info-box p {
    color: #555;
    line-height: 1.6;
}

/* Balloons */
.balloons-container {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
    z-index: 9999;
    overflow: hidden;
}

.balloon {
    position: absolute;
    bottom: -150px;
    font-size: 60px;
    animation: rise 4s ease-in forwards;
    filter: drop-shadow(0 5px 10px rgba(0, 0, 0, 0.3));
}

@keyframes rise {
    0% {
        bottom: -150px;
        opacity: 1;
        transform: translateX(0) rotate(0deg);
    }
    100% {
        bottom: 110vh;
        opacity: 0;
        transform: translateX(var(--drift, 0px)) rotate(var(--rotate, 0deg));
    }
}

/* Responsive */
@media (max-width: 768px) {
    .number-line {
        flex-wrap: wrap;
        gap: 15px;
    }

    .number-item {
        min-width: 70px;
    }

    .number-input,
    .number-item.filled {
        font-size: 16px;
        padding: 12px 5px;
    }

    h1 {
        font-size: 24px;
    }

    .timeline {
        display: none;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 20px;
    }

    .number-line {
        gap: 10px;
    }

    .number-item {
        min-width: 50px;
    }
}