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

body {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    padding: 20px;
    transition: background 0.3s ease;
}

body.dark-theme {
    background: linear-gradient(135deg, #2c3e50 0%, #34495e 100%);
}

.calculator {
    background: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(20px);
    border-radius: 20px;
    border: 1px solid rgba(255, 255, 255, 0.2);
    padding: 25px;
    width: 100%;
    max-width: 400px;
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.15);
}

.header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 15px;
}

.title {
    color: white;
    font-size: 1.5rem;
    font-weight: 600;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
}

.theme {
    background: rgba(255, 255, 255, 0.2);
    border: none;
    border-radius: 50%;
    width: 45px;
    height: 45px;
    font-size: 1.2rem;
    cursor: pointer;
    color: white;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    justify-content: center;
}

.theme:hover {
    background: rgba(255, 255, 255, 0.3);
    transform: scale(1.05);
}

.mode{
    flex: 1;
    padding: 10px 15px;
    background: transparent;
    color: rgba(255, 255, 255, 0.7);
    margin-bottom: 10px ;
    border: none;
    border-radius: 12px;
    font-size: 42px;
    font-weight: 500;
    transition: all 0.3s ease;
     background: rgba(255, 255, 255, 0.25);
    font-weight: 600;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.2);
    text-align: center;
}
.display {
    background: rgba(0, 0, 0, 0.8);
    color: white;
    border-radius: 15px;
    padding: 20px;
    margin-bottom: 15px;
    min-height: 80px;
    position: relative;
}

.expression {
    font-size: 0.9rem;
    color: rgba(255, 255, 255, 0.7);
    margin-bottom: 5px;
    min-height: 20px;
    text-align: right;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.result {
    font-size: 2.2rem;
    text-align: right;
    font-weight: 300;
    letter-spacing: 1px;
    word-wrap: break-word;
    overflow: hidden;
}
.scientific-functions {
    display: none;
    grid-template-columns: repeat(4, 1fr);
    gap: 8px;
    margin-bottom: 15px;
}

.scientific-functions.active {
    display: grid;
}
.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-template-rows: repeat(5, 1fr);
    gap: 10px;
    grid-template-areas:
        "ac c back div"
        "seven eight nine mult"
        "four five six sub"
        "one two three add"
        "zero zero dot equals";
}
.buttons > button:nth-child(1) { grid-area: ac; }
.buttons > button:nth-child(2) { grid-area: c; }
.buttons > button:nth-child(3) { grid-area: back; }
.buttons > button:nth-child(4) { grid-area: div; }

.buttons > button:nth-child(5) { grid-area: seven; }
.buttons > button:nth-child(6) { grid-area: eight; }
.buttons > button:nth-child(7) { grid-area: nine; }
.buttons > button:nth-child(8) { grid-area: mult; }

.buttons > button:nth-child(9) { grid-area: four; }
.buttons > button:nth-child(10) { grid-area: five; }
.buttons > button:nth-child(11) { grid-area: six; }
.buttons > button:nth-child(12) { grid-area: sub; }

.buttons > button:nth-child(13) { grid-area: one; }
.buttons > button:nth-child(14) { grid-area: two; }
.buttons > button:nth-child(15) { grid-area: three; }
.buttons > button:nth-child(16) { grid-area: add; }

.buttons > button:nth-child(17) { grid-area: zero; }
.buttons > button:nth-child(18) { grid-area: dot; }
.buttons > button:nth-child(19) { grid-area: equals; }
button {
    padding: 12px;
    border-radius: 12px;
    border: none;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    color: white;
    transition: all 0.2s ease;
    position: relative;
    overflow: hidden;
    min-height: 45px;
}

button:hover {
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.3);
}

button:active {
    transform: translateY(0);
}

.number {
    background: rgba(255, 255, 255, 0.15);
    backdrop-filter: blur(10px);
}

.number:hover {
    background: rgba(255, 255, 255, 0.25);
}
.operator {
    background: rgba(255, 159, 10, 0.9);
    font-weight: 700;
}

.operator:hover {
    background: rgba(255, 159, 10, 1);
}
.function {
    background: rgba(52, 152, 219, 0.8);
    font-size: 0.8rem;
}

.function:hover {
    background: rgba(52, 152, 219, 1);
}
.clear {
    background: rgba(255, 69, 58, 0.8);
    font-weight: 700;
}

.clear:hover {
    background: rgba(255, 69, 58, 1);
}
.equals {
    background: linear-gradient(45deg, #ff6b6b, #feca57);
    font-weight: 700;
    font-size: 1.3rem;
}

.equals:hover {
    background: linear-gradient(45deg, #ff5252, #ffc107);
}
.scientific-functions button {
    padding: 10px;
    font-size: 0.75rem;
    min-height: 40px;
}
.result.error {
    color: #ff6b6b !important;
    animation: shake 0.5s ease-in-out;
}

@keyframes shake {
    0%, 100% { transform: translateX(0); }
    25% { transform: translateX(-5px); }
    75% { transform: translateX(5px); }
}
@media (max-width: 480px) {
    .calculator {
        padding: 20px;
        max-width: 360px;
    }
    
    .result {
        font-size: 1.8rem;
    }
    
    button {
        padding: 10px;
        font-size: 0.9rem;
        min-height: 40px;
    }
    
    .scientific-functions button {
        padding: 8px;
        font-size: 0.7rem;
        min-height: 35px;
    }
}