* {
    box-sizing: border-box;
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
}

body {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    background: linear-gradient(to right, #6dd5ed, #2193b0);
    color: #fff;
}

/* Header styling - slightly different from background */
header {
    width: 100vw;
    text-align: center;
    font-size: 1.5em;
    font-weight: bold;
    padding: 20px 0;
    background: rgba(33, 147, 176, 0.8); /* slightly darker */
    color: #fff;
}

/* Footer styling - slightly different from background */
footer {
    width: 100vw;
    text-align: center;
    font-size: 1em;
    padding: 20px 0;
    background: rgba(33, 147, 176, 0.8); /* slightly darker */
    color: #fff;
}

/* Main content between header and footer */
main {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 20px 10px;
    width: 100%;
}

/* Input field with centered numbers */
input {
    padding: 12px;
    margin: 5px 0;
    width: 100%;
    border-radius: 5px;
    border: none;
    font-size: 1.5em;
    text-align: center;
}

/* Select and buttons */
select, button {
    padding: 12px;
    margin: 5px 0;
    width: 100%;
    border-radius: 5px;
    border: none;
    font-size: 1.2em;
}

button#convertBtn {
    cursor: pointer;
    background-color: #ffb347;
    color: #000;
    font-weight: bold;
    transition: 0.3s;
}

button#convertBtn:hover {
    background-color: #ffcc70;
}

/* Result display */
.result {
    margin: 15px 0;
    font-size: 1.3em;
    font-weight: bold;
    text-align: center;
    width: 90%;
}

/* Keyboard styling */
.keyboard {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 10px;
    width: 90%;
    max-width: 400px;
    margin-top: 10px;
}

.keyboard .key {
    padding: 15px;
    font-size: 1.2em;
    border-radius: 5px;
    background-color: rgba(255, 255, 255, 0.2);
    color: #fff;
    border: none;
    cursor: pointer;
    text-align: center;
}

.keyboard .key:hover {
    background-color: rgba(255, 255, 255, 0.4);
}

/* Clear button full row */
#clear {
    grid-column: span 3;
    background-color: #ff6666;
}

#clear:hover {
    background-color: #ff4c4c;
}

@media(max-width: 500px) {
    input, select, button {
        font-size: 1em;
    }

    .keyboard .key {
        padding: 12px;
        font-size: 1em;
    }
}