* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
}

body {
    background: linear-gradient(135deg, #f5f5f5 0%, #ffffff 100%);
    min-height: 100vh;
}

.wrapper {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.container {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 2rem;
    text-align: center;
}

.content-box {
    background: rgba(255, 255, 255, 0.9);
    border-radius: 20px;
    box-shadow: 0 8px 30px rgba(0, 0, 0, 0.1);
    backdrop-filter: blur(10px);
    max-width: 500px;
    width: 100%;
    padding: 2rem;
}

h1 {
    font-size: 2.5rem;
    color: #000;
    margin-bottom: 0.8rem;
    font-weight: 700;
}

h2 {
    font-size: 1.5rem;
    color: #666;
    margin-bottom: 2rem;
    font-weight: 500;
}

.input-container {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    margin-bottom: 1rem;
    width: 100%;
}

.input-container > * {
    width: 100%;
}

.input-container button {
    margin-top: 0.5rem;
}

.cf-inputs {
    display: flex;
    gap: 0.5rem;
    width: 100%;
}

.cf-inputs input {
    flex: 1;
}

#problemLetter {
    flex: 0.5;
    text-transform: uppercase;
}

input {
    padding: 1rem;
    border: 2px solid #eaeaea;
    border-radius: 10px;
    font-size: 1rem;
    transition: all 0.3s ease;
    outline: none;
}

input:focus {
    border-color: #000;
}

input.error {
    border-color: #ff3b30;
    animation: shake 0.82s cubic-bezier(.36,.07,.19,.97) both;
    transform: translate3d(0, 0, 0);
}

button {
    padding: 1rem 2rem;
    background: #000;
    color: #fff;
    border: none;
    border-radius: 10px;
    font-size: 1rem;
    cursor: pointer;
    transition: all 0.3s ease;
}

button:hover {
    background: #333;
    transform: translateY(-2px);
}

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

.platform-btn {
    padding: 0.5rem 1.5rem;
    background: transparent;
    color: #666;
    border: 2px solid #eaeaea;
    border-radius: 8px;
    font-size: 1rem;
    cursor: pointer;
    transition: all 0.3s ease;
}

.platform-btn:hover {
    background: rgba(0, 0, 0, 0.05);
    transform: translateY(-1px);
}

.platform-btn.active {
    background: #000;
    color: #fff;
    border-color: #000;
}

.hint {
    color: #666;
    font-size: 0.9rem;
    margin-top: 1rem;
}

@keyframes shake {
    10%, 90% { transform: translate3d(-1px, 0, 0); }
    20%, 80% { transform: translate3d(2px, 0, 0); }
    30%, 50%, 70% { transform: translate3d(-4px, 0, 0); }
    40%, 60% { transform: translate3d(4px, 0, 0); }
}

@media (max-width: 600px) {
    .input-container {
        flex-direction: column;
    }
    
    .container {
        padding: 1.5rem;
    }
    
    h1 {
        font-size: 2rem;
    }
}

footer {
    text-align: center;
    padding: 1rem;
    color: #666;
    font-size: 0.9rem;
    backdrop-filter: blur(10px);
}

footer a {
    color: #000;
    text-decoration: none;
    transition: opacity 0.3s ease;
}

footer a:hover {
    opacity: 0.7;
}