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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    min-height: 100vh;
    background: linear-gradient(135deg, #83e4e2 0%, #a2b6ff 100%);
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
}

.container {
    max-width: 600px;
    width: 100%;
    text-align: center;
}

h1 {
    color: #2c3e50;
    margin-bottom: 2rem;
    font-size: 2.5rem;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.1);
}

.problem-card {
    background: white;
    padding: 2rem;
    border-radius: 15px;
    box-shadow: 0 10px 20px rgba(0,0,0,0.1);
}

#problem-text {
    font-size: 1.3rem;
    margin-bottom: 1.5rem;
    color: #34495e;
    line-height: 1.6;
}

.input-section {
    display: flex;
    gap: 10px;
    margin-bottom: 1rem;
    justify-content: center;
}

input {
    padding: 10px;
    font-size: 1.1rem;
    border: 2px solid #ddd;
    border-radius: 8px;
    width: 150px;
}

button {
    padding: 10px 20px;
    font-size: 1rem;
    border: none;
    border-radius: 8px;
    background: #3498db;
    color: white;
    cursor: pointer;
    transition: transform 0.1s;
}

button:hover {
    transform: scale(1.05);
}

#next-button {
    background: #2ecc71;
    margin-top: 1rem;
}

#feedback {
    min-height: 24px;
    margin: 1rem 0;
    font-weight: bold;
}

.feedback-correct {
    color: #2ecc71;
}

.feedback-incorrect {
    color: #e74c3c;
}

.score {
    margin-top: 2rem;
    font-size: 1.2rem;
    color: #2c3e50;
    font-weight: bold;
}

.info-bar {
    background: white;
    padding: 1rem;
    border-radius: 10px;
    margin-bottom: 1rem;
    display: flex;
    justify-content: space-between;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}

#timer {
    font-family: monospace;
    font-size: 1.2rem;
    font-weight: bold;
    color: #e74c3c;
}

#progress {
    font-weight: bold;
    color: #2c3e50;
}