body {
    font-family: Arial, sans-serif;
    margin: 20px;
    background-color: #f0f8ff;
    color: #333;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    padding: 0 10px;
}
.container {
    max-width: 400px;
    width: 90%;
    background: white;
    padding: 30px;
    border-radius: 12px;
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.15);
    border: 2px solid #6495ed;
}
h2 {
    text-align: center;
    color: #1e90ff;
    margin-bottom: 25px;
}
label {
    display: block;
    margin-top: 15px;
    font-weight: 600;
    color: #555;
}
.input-hint {
    font-size: 0.8em;
    color: #777;
    margin-top: 5px;
    margin-bottom: 5px;
}
input[type="number"] {
    width: 100%;
    padding: 12px;
    margin-top: 8px;
    margin-bottom: 20px;
    border: 1px solid #ccc;
    border-radius: 6px;
    box-sizing: border-box;
    transition: border-color 0.3s;
}
input[type="number"]:focus {
    border-color: #1e90ff;
    outline: none;
}
button {
    width: 100%;
    background-color: #1e90ff;
    color: white;
    padding: 12px;
    border: none;
    border-radius: 6px;
    cursor: pointer;
    font-size: 17px;
    font-weight: bold;
    transition: background-color 0.3s, transform 0.1s;
}
button:hover {
    background-color: #007bff;
}
button:active {
    transform: translateY(1px);
}
#result-output {
    margin-top: 30px;
    padding: 15px;
    border-radius: 8px;
    text-align: center;
    font-size: 1.1em;
    display: none;
}
.error {
    background-color: #ffe0e0;
    color: #cc0000;
    border: 1px solid #ffaaaa;
}
.success {
    background-color: #e6ffe6;
    color: #008000;
    border: 1px solid #c8f5c8;
}

@media (max-width: 900px) {
    .container {
        max-width: 480px;
        padding: 24px;
    }
}

@media (max-width: 600px) {
    body {
        margin: 0; 
        align-items: flex-start; 
        min-height: auto;
        padding-top: 20px;
        padding-bottom: 20px; 
    }
    .container {
        max-width: 100%;
        width: calc(100% - 40px); 
        margin: 0 auto;
        padding: 20px;
        border-radius: 10px;
        box-shadow: 0 6px 14px rgba(0, 0, 0, 0.12);
        border-width: 1px;
    }
    h2 {
        font-size: 1.4rem;
        margin-bottom: 18px;
    }
    label {
        font-size: 0.95rem;
        margin-top: 12px;
    }
    .input-hint {
        font-size: 0.75rem;
    }
    input[type="number"] {
        padding: 10px;
        font-size: 1rem;
    }
    button {
        padding: 11px;
        font-size: 16px;
    }
    #result-output {
        font-size: 1rem;
        margin-top: 18px;
        padding: 12px;
    }
}

@media (max-width: 400px) {
    .container {
        padding: 15px;
        border-radius: 8px;
        width: calc(100% - 30px);
    }
    h2 {
        font-size: 1.2rem;
    }
    input[type="number"] {
        padding: 9px;
    }
    button {
        font-size: 15px;
        padding: 10px;
    }
    label, .input-hint {
        font-size: 0.9rem;
    }
}