body {
    background-color: #f6f9fc;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    color: #1d1d1f;
    margin: 0;
    padding: 0;
}

.container {
    max-width: 480px;
    margin: 100px auto;
    padding: 40px;
    background-color: #ffffff;
    box-shadow: 0 0 20px rgba(0,0,0,0.05);
    border-radius: 8px;
    text-align: center;
}

h1 {
    font-size: 26px;
    margin-bottom: 10px;
    color: #202124;
}

p {
    font-size: 15px;
    color: #5f6368;
}

.challenge {
    margin-top: 30px;
}

.checkbox-wrapper {
    display: inline-flex;
    align-items: center;
    cursor: pointer;
    font-size: 16px;
    user-select: none;
    margin: 20px 0;
}

.checkbox-wrapper input {
    display: none;
}

.checkmark {
    height: 24px;
    width: 24px;
    background-color: #fff;
    border: 2px solid #ccc;
    border-radius: 4px;
    margin-right: 10px;
    position: relative;
}

.checkbox-wrapper input:checked + .checkmark::after {
    content: "";
    position: absolute;
    left: 7px;
    top: 2px;
    width: 6px;
    height: 12px;
    border: solid #1a73e8;
    border-width: 0 2px 2px 0;
    transform: rotate(45deg);
}

.spinner {
    margin-top: 20px;
    border: 4px solid #e0e0e0;
    border-top: 4px solid #1a73e8;
    border-radius: 50%;
    width: 32px;
    height: 32px;
    animation: spin 1s linear infinite;
    margin-left: auto;
    margin-right: auto;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

.footer {
    margin-top: 40px;
    font-size: 13px;
    color: #9e9e9e;
}

.logo {
    max-width: 180px;
    margin-bottom: 20px;
}