:root {
    --primary-color: #3498db;
    --dark-bg: #2c3e50;
    --light-text: #ffffff;
    --dark-text: #2c3e50;
    --calculator-bg: #ffffff;
    --button-bg: #f1f3f4;
}

@media (prefers-color-scheme: dark) {
    :root {
        --primary-color: #2980b9;
        --dark-bg: #1a1a1a;
        --light-text: #ffffff;
        --dark-text: #ffffff;
        --calculator-bg: #2d2d2d;
        --button-bg: #3d3d3d;
    }
}

/* Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
    background: #f8f9fa;
    min-height: 100vh;
    position: relative;
    padding-bottom: 60px;
    color: var(--dark-text);
}

header {
    background: var(--calculator-bg);
    padding: 20px;
    text-align: center;
    box-shadow: 0 2px 15px rgba(0,0,0,0.1);
}

.logo {
    height: 80px;
    width: auto;
    filter: drop-shadow(0 2px 4px rgba(0,0,0,0.1));
    margin-bottom: 10px;
}

.app-name {
    color: var(--dark-text);
    font-size: 2em;
    font-weight: 600;
    letter-spacing: -0.5px;
    margin-bottom: 5px;
}

.container {
    max-width: 800px;
    margin: 40px auto;
    padding: 30px;
    background: var(--calculator-bg);
    border-radius: 15px;
    box-shadow: 0 5px 25px rgba(0,0,0,0.08);
}

.converter-section {
    display: grid;
    grid-template-columns: 1fr 1fr 1fr auto auto;
    gap: 15px;
    margin-bottom: 30px;
}

@media (max-width: 768px) {
    .converter-section {
        grid-template-columns: 1fr;
    }
}

input, select {
    padding: 12px 15px;
    border: 1px solid #e0e0e0;
    border-radius: 8px;
    font-size: 16px;
    background: var(--button-bg);
    color: var(--dark-text);
    transition: border-color 0.3s;
}

.currency-select {
    background: var(--button-bg);
    color: var(--dark-text);
}

input:focus, select:focus {
    border-color: var(--primary-color);
    outline: none;
}

button {
    background: var(--primary-color);
    color: var(--light-text);
    border: none;
    padding: 12px 25px;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.3s;
    font-weight: 500;
}

button:hover {
    background: #2980b9;
    transform: translateY(-1px);
}

#result {
    font-size: 26px;
    font-weight: 600;
    color: #2ecc71;
    text-align: center;
    margin: 25px 0;
    padding: 15px;
    background: var(--button-bg);
    border-radius: 8px;
}

.calculator-modal {
    display: none;
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background: var(--calculator-bg);
    padding: 20px;
    border-radius: 15px;
    box-shadow: 0 10px 50px rgba(0,0,0,0.2);
    z-index: 1000;
    width: 350px;
}

.modal-overlay {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,0.5);
    z-index: 999;
}

footer {
    background: #f9f9f9; /* Light background */
    color: #333; /* Darker text for readability */
    padding: 20px;
    text-align: center;
    position: fixed;
    bottom: 0;
    width: 100%;
    font-size: 14px;
    box-shadow: 0 -2px 5px rgba(0, 0, 0, 0.1); /* Optional: subtle shadow for separation */
}


.error {
    color: #e74c3c;
    text-align: center;
    margin: 15px 0;
    font-weight: 500;
}

/* Calculator Styles */
#calculator {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
    margin-top: 15px;
}

.calc-btn {
    padding: 15px;
    border: none;
    background: var(--button-bg);
    color: var(--dark-text);
    border-radius: 5px;
    cursor: pointer;
    font-size: 16px;
    transition: all 0.2s;
    user-select: none;
}

.calc-btn:hover {
    background: #e0e0e0;
}

.calc-btn:active {
    transform: scale(0.95);
}

.calc-display {
    grid-column: span 4;
    padding: 15px;
    background: var(--button-bg);
    color: var(--dark-text);
    border-radius: 8px;
    text-align: right;
    font-size: 24px;
    margin-bottom: 10px;
    overflow: hidden;
    text-overflow: ellipsis;
}

.scientific {
    display: none;
}

.calc-operator {
    background: #dfe6e9;
}

.calc-equal {
    background: var(--primary-color);
    color: var(--light-text);
}

.calc-equal:hover {
    background: #2980b9;
}

.mode-toggle {
    grid-column: span 2;
    background: var(--dark-bg);
    color: var(--light-text);
}

.clear-btn {
    background: #e74c3c;
    color: var(--light-text);
}

.clear-btn:hover {
    background: #c0392b;
}