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

html, body {
    height: 100%; 
}

body {
    background-color: #000; 
    color: #f0f0f0; 
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    display: flex;
    justify-content: center; 
    align-items: flex-start;
    padding: 100px 20px 20px 20px; 
    
    background-image: linear-gradient(rgba(0,0,0, 0.7), rgba(0,0,0, 0.7)), url('../img/yellow_oil.jpg');
    background-size: cover;
    background-position: center center;
    background-attachment: fixed;
}

.calculator-container {
    width: 100%;
    max-width: 450px; 
    text-align: center;
    padding: 0; 
    margin: 20px;
    position: relative; 
}

.dark-box {
    background-color: rgba(0, 0, 0, 0.6); 
    border: 1px solid rgba(255, 255, 255, 0.2); 
    border-radius: 12px; 
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.5); 
}

.window-header {
    display: flex;
    justify-content: center; 
    align-items: center; 
    padding: 8px 15px 8px 6px; 
    
    background-color: rgba(45, 45, 45, 0.9); 
    color: #f0f0f0;
    font-size: 0.9rem;
    font-weight: 500;
    
    letter-spacing: 1px;
    
    border-top-left-radius: 12px;
    border-top-right-radius: 12px;
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.window-icon {
    width: 20px; 
    height: 20px; 
    margin-right: 7px;
}

.window-title {
    user-select: none;
    flex-grow: 1; 
    text-align: left;
}

.input-wrapper, #resultOutput {
    padding: 0 25px;
}

.input-wrapper {
    display: flex;
    flex-direction: column;
    gap: 10px; 
    margin-bottom: 25px;
    padding-top: 25px; 
}

#literInput {
    font-size: 1.1rem;
    padding: 16px;
    background-color: #222; 
    border: 1px solid #444; 
    color: #fff; 
    border-radius: 8px; 
    width: 100%;
}

#literInput::placeholder {
    color: #777;
    opacity: 1; 
}

#calculateButton {
    font-size: 1.1rem;
    font-weight: bold;
    padding: 16px;
    background-color: #FFB800; 
    color: #000;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    transition: background-color 0.2s ease; 
}

#calculateButton:hover {
    background-color: #cc9300; 
}

#resultOutput {
    font-size: 1.8rem;
    font-weight: bold;
    color: #FFB800; 
    margin-bottom: 25px;
}

@media (min-width: 600px) {
    .input-wrapper {
        flex-direction: row; 
    }

    #literInput {
        flex-grow: 1; 
        border-top-right-radius: 0;
        border-bottom-right-radius: 0;
    }

    #calculateButton {
        border-top-left-radius: 0;
        border-bottom-left-radius: 0;
    }
}