@import url('https://fonts.googleapis.com/css2?family=Orbitron:wght@400;500;600;700&family=Roboto+Mono:wght@300;400;500&display=swap');

:root {
    --primary-red: #0e45dd;
    --dark-red: #042bd9d5;
    --light-red: #fffefe;
    --black: #1a1a1a;
    --dark-gray: #2b2d42;
    --medium-gray: #8d99ae;
    --light-gray: #edf2f4;
    --white: #ffffff;
    --gradient: linear-gradient(135deg, var(--primary-red), var(--dark-red));
}

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

body {
    font-family: 'Roboto Mono', monospace;
    background-color: var(--black);
    color: var(--light-gray);
    line-height: 1.6;
}

header {
    background: var(--gradient);
    color: var(--white);
    padding: 1.5rem 0;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
    position: relative;
}

.header-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

header h1 {
    margin: 0;
    font-size: 2rem;
    font-weight: 600;
    text-shadow: 1px 1px 3px rgba(0, 0, 0, 0.5);
    font-family: 'Orbitron', sans-serif;
}

.back-btn {
    color: var(--white);
    text-decoration: none;
    font-weight: 500;
    padding: 0.5rem 1rem;
    border-radius: 5px;
    transition: background-color 0.3s;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    background-color: rgba(0, 0, 0, 0.3);
}

.back-btn:hover {
    background-color: rgba(0, 0, 0, 0.5);
}

.calculator-container {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: calc(100vh - 100px);
    padding: 2rem 1rem;
    background: linear-gradient(rgba(0, 0, 0, 0.7), rgba(0, 0, 0, 0.7)), 
                url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" width="100" height="100" viewBox="0 0 100 100"><rect width="100" height="100" fill="%231a1a1a"/><path d="M0 0L100 100" stroke="%23d90429" stroke-width="1" opacity="0.1"/><path d="M100 0L0 100" stroke="%23d90429" stroke-width="1" opacity="0.1"/></svg>');
}

.calculator {
    background: var(--dark-gray);
    border-radius: 15px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.5);
    width: 100%;
    max-width: 400px;
    overflow: hidden;
    border: 1px solid rgba(0, 0, 0, 0.1);
}

.display {
    padding: 1.5rem;
    text-align: right;
    background: var(--black);
    color: var(--light-gray);
    border-bottom: 2px solid var(--primary-red);
    min-height: 120px;
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
}

.previous-operand {
    font-size: 1.2rem;
    color: var(--medium-gray);
    min-height: 1.5rem;
    font-family: 'Roboto Mono', monospace;
    margin-bottom: 0.5rem;
}

.current-operand {
    font-size: 2.5rem;
    word-wrap: break-word;
    font-family: 'Orbitron', sans-serif;
    color: var(--white);
    text-shadow: 0 0 5px rgba(255, 255, 255, 0.3);
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 1px;
    background: rgba(0, 0, 0, 0.2);
}

.buttons > button {
    border: none;
    padding: 1.5rem;
    font-size: 1.2rem;
    cursor: pointer;
    background: rgba(0, 0, 0, 0.5);
    color: var(--light-gray);
    transition: all 0.2s;
    font-family: 'Orbitron', sans-serif;
    font-weight: 500;
}

.buttons > button:hover {
    background: rgba(0, 0, 0, 0.7);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.3);
}

.buttons > button:active {
    transform: translateY(0);
    box-shadow: none;
}

.buttons > button[data-action] {
    background: rgba(0, 0, 0, 0.6);
}

.buttons > button[data-action="add"],
.buttons > button[data-action="subtract"],
.buttons > button[data-action="multiply"],
.buttons > button[data-action="divide"] {
    background: var(--primary-red);
    color: var(--white);
    font-size: 1.4rem;
}

.buttons > button[data-action="add"]:hover,
.buttons > button[data-action="subtract"]:hover,
.buttons > button[data-action="multiply"]:hover,
.buttons > button[data-action="divide"]:hover {
    background: var(--dark-red);
}

.buttons > button[data-action="clear"],
.buttons > button[data-action="delete"] {
    background: rgba(0, 0, 0, 0.3);
    color: var(--light-red);
}

.buttons > button[data-action="clear"]:hover,
.buttons > button[data-action="delete"]:hover {
    background:rgba(255, 255, 255, 0.05);
}

.buttons > button[data-action="calculate"] {
    background: var(--gradient);
    color: var(--white);
    font-size: 1.4rem;
}

.buttons > button[data-action="calculate"]:hover {
    background: linear-gradient(135deg, var(--dark-red), var(--primary-red));
    box-shadow: 0 4px 12px rgba(230, 57, 70, 0.4);
}

.buttons > button[data-number] {
    background: rgba(255, 255, 255, 0.05);
}

.buttons > button[data-number]:hover {
    background: rgba(255, 255, 255, 0.1);
}

.span-two {
    grid-column: span 2;
}

/* Animation for button presses */
@keyframes buttonPress {
    0% { transform: scale(1); }
    50% { transform: scale(0.95); }
    100% { transform: scale(1); }
}

.buttons > button:active {
    animation: buttonPress 0.1s ease;
}

@media (max-width: 480px) {
    .calculator {
        max-width: 100%;
    }
    
    .buttons > button {
        padding: 1.2rem;
        font-size: 1.1rem;
    }
    
    .current-operand {
        font-size: 2rem;
    }
    
    header h1 {
        font-size: 1.5rem;
    }
    
    .header-content {
        flex-direction: column;
        gap: 1rem;
    }
    
    .back-btn {
        position: static;
        transform: none;
    }
}