/* style.css */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
body {
    font-family: 'Inter', sans-serif;
    background: linear-gradient(135deg, #0a0f1e 0%, #0a0c14 100%);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
    transition: background 0.3s, color 0.3s;
}
body.light {
    background: linear-gradient(135deg, #e0e5f0, #f5f7fc);
}
.calculator-container {
    display: flex;
    flex-wrap: wrap;
    gap: 30px;
    max-width: 900px;
    width: 100%;
    justify-content: center;
    align-items: flex-start;
}
.calculator {
    background: rgba(20, 25, 40, 0.8);
    backdrop-filter: blur(16px);
    border-radius: 32px;
    padding: 24px;
    box-shadow: 0 25px 45px -12px rgba(0, 0, 0, 0.4);
    border: 1px solid rgba(255, 255, 255, 0.1);
    width: 100%;
    max-width: 460px;
    transition: all 0.3s;
}
body.light .calculator {
    background: rgba(255, 255, 255, 0.9);
    border-color: rgba(0, 0, 0, 0.08);
    box-shadow: 0 15px 35px rgba(0, 0, 0, 0.1);
}
.theme-toggle {
    position: absolute;
    top: 20px;
    right: 20px;
    display: flex;
    align-items: center;
    gap: 12px;
    color: #fff;
}
body.light .theme-toggle {
    color: #1e293b;
}
.switch {
    position: relative;
    display: inline-block;
    width: 52px;
    height: 26px;
}
.switch input {
    opacity: 0;
    width: 0;
    height: 0;
}
.slider {
    position: absolute;
    cursor: pointer;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: #3b82f6;
    transition: 0.3s;
    border-radius: 34px;
}
.slider:before {
    position: absolute;
    content: "";
    height: 20px;
    width: 20px;
    left: 3px;
    bottom: 3px;
    background-color: white;
    transition: 0.3s;
    border-radius: 50%;
}
input:checked + .slider {
    background-color: #f59e0b;
}
input:checked + .slider:before {
    transform: translateX(26px);
}
.display-area {
    background: rgba(0, 0, 0, 0.3);
    border-radius: 24px;
    padding: 20px;
    margin-bottom: 24px;
    text-align: right;
    word-wrap: break-word;
    word-break: break-all;
}
body.light .display-area {
    background: #f1f5f9;
}
.expression {
    font-size: 2rem;
    font-weight: 500;
    color: #f1f5f9;
    min-height: 3rem;
}
body.light .expression {
    color: #0f172a;
}
.result {
    font-size: 1.2rem;
    color: #94a3b8;
    margin-top: 8px;
}
body.light .result {
    color: #475569;
}
.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 12px;
}
.btn {
    background: rgba(255, 255, 255, 0.08);
    border: none;
    border-radius: 24px;
    padding: 16px 0;
    font-size: 1.3rem;
    font-weight: 600;
    color: #f8fafc;
    cursor: pointer;
    transition: all 0.15s;
    font-family: inherit;
}
body.light .btn {
    background: #eef2ff;
    color: #0f172a;
    box-shadow: 0 2px 4px rgba(0,0,0,0.02);
}
.btn:hover {
    background: #3b82f6;
    color: white;
    transform: scale(0.98);
}
.btn.function {
    background: rgba(59, 130, 246, 0.2);
    color: #60a5fa;
}
body.light .btn.function {
    background: #dbeafe;
    color: #2563eb;
}
.btn.operator {
    background: rgba(245, 158, 11, 0.2);
    color: #fbbf24;
}
body.light .btn.operator {
    background: #fffbeb;
    color: #d97706;
}
.btn.equals {
    background: linear-gradient(135deg, #3b82f6, #9333ea);
    color: white;
}
.btn.equals:hover {
    filter: brightness(1.05);
}
.history-panel {
    background: rgba(20, 25, 40, 0.7);
    backdrop-filter: blur(12px);
    border-radius: 28px;
    padding: 20px;
    width: 260px;
    border: 1px solid rgba(255,255,255,0.1);
    transition: all 0.3s;
}
body.light .history-panel {
    background: rgba(255,255,255,0.8);
    border-color: rgba(0,0,0,0.05);
}
.history-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 16px;
    color: #cbd5e1;
}
body.light .history-header {
    color: #1e293b;
}
.clear-history-btn {
    background: none;
    border: none;
    color: #f97316;
    cursor: pointer;
    font-size: 0.8rem;
    font-weight: 500;
}
#historyList {
    list-style: none;
    max-height: 400px;
    overflow-y: auto;
}
#historyList li {
    padding: 8px 0;
    border-bottom: 1px solid rgba(255,255,255,0.1);
    font-size: 0.9rem;
    color: #cbd5e6;
    word-break: break-word;
}
body.light #historyList li {
    border-bottom-color: rgba(0,0,0,0.05);
    color: #334155;
}
.empty-history {
    color: #6b7280;
    text-align: center;
    font-style: italic;
}
@media (max-width: 700px) {
    .calculator-container {
        flex-direction: column;
        align-items: center;
    }
    .history-panel {
        width: 100%;
        max-width: 460px;
    }
    .theme-toggle {
        top: 10px;
        right: 10px;
    }
}