:root {
            --bg-color: #f8f9fa;
            --main-border: #000000;
            --box-bg: rgba(255, 255, 255, 0.35);
            --active-bg: rgba(0, 0, 0, 0.15);
            --text-color: #000000;
            --line-color: #000000;
            --font-main: 'Times New Roman', Times, serif;
            --glass-blur: blur(50px);
            --glass-border: 1px solid rgba(0, 0, 0, 0.2);
            --glass-shadow: 0 8px 32px rgba(0, 0, 0, 0.08);
        }

        body {
            font-family: var(--font-main);
            color: var(--text-color);
            margin: 0;
            padding: 0;
            display: flex;
            justify-content: center;
            align-items: center;
            width: 100vw;
            min-height: 100vh;
            overflow: auto;
            user-select: none;
            background: linear-gradient(135deg, #f9f9fb, #f4f7fa, #f7f9f6, #f5f8fc, #f8f7fa);
            background-size: 400% 400%;
            animation: pastelShift 100s ease infinite;
        }

        @keyframes pastelShift {
            0% {
                background-position: 0% 50%;
            }

            50% {
                background-position: 100% 50%;
            }

            100% {
                background-position: 0% 50%;
            }
        }

        .container {
            position: relative;
            width: 1150px;
            height: 950px;
            background: transparent;
            border: none;
            box-shadow: none;
            margin: 0 auto;
        }

        .circuit-wrapper {
            position: absolute;
            top: 40px;
            left: 95px;
            width: 1000px;
            height: 800px;
        }

        /* SVG for drawing connecting lines */
        #connections {
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            pointer-events: none;
            z-index: 1;
            overflow: visible;
        }

        line,
        polyline,
        path {
            stroke: var(--line-color);
            stroke-width: 1.5;
            fill: none;
        }

        .arrowhead {
            fill: var(--line-color);
        }

        /* The Main ALU Enclosure */
        .alu-enclosure {
            position: absolute;
            top: 50px;
            left: 200px;
            width: 650px;
            height: 700px;
            border: 2px solid rgba(0, 0, 0, 0.3);
            z-index: 2;
            background: rgba(255, 255, 255, 0.15);
            backdrop-filter: var(--glass-blur);
            -webkit-backdrop-filter: var(--glass-blur);
            border-radius: 16px;
            box-shadow: var(--glass-shadow);
        }

        /* Inner blocks (Arithmetic, Logic, Mux) */
        .block {
            position: absolute;
            background: rgba(200, 220, 255, 0.3);
            border: 2px solid rgba(0, 0, 0, 0.25);
            display: flex;
            justify-content: center;
            align-items: center;
            font-weight: bold;
            font-size: 1.2rem;
            backdrop-filter: blur(8px);
            -webkit-backdrop-filter: blur(8px);
            border-radius: 12px;
            box-shadow: var(--glass-shadow);
            text-align: center;
        }

        .arithmetic-unit {
            top: 20px;
            left: 20px;
            width: 400px;
            height: 280px;
        }

        .logic-unit {
            bottom: 20px;
            left: 20px;
            width: 400px;
            height: 280px;
        }

        .multiplexer {
            position: absolute;
            right: 40px;
            width: 100px;
            height: 400px;
            writing-mode: vertical-rl;
            text-orientation: mixed;
            transform: rotate(180deg);
        }

        .pill-shape {
            background: rgba(255, 255, 255, 0.5);
            border-radius: 20px;
            padding: 10px 30px;
            border: 1px solid rgba(0, 0, 0, 0.2);
            box-shadow: 0 4px 15px rgba(0, 0, 0, 0.08);
            font-weight: normal;
            backdrop-filter: blur(6px);
            -webkit-backdrop-filter: blur(6px);
        }

        /* Input / Output Nodes that look like text logic operators */
        .io-node {
            position: absolute;
            font-size: 1rem;
            cursor: pointer;
            display: flex;
            align-items: center;
            gap: 5px;
            z-index: 10;
        }

        .io-label {
            font-weight: bold;
        }

        .io-value {
            width: 25px;
            height: 25px;
            border: 1px solid var(--main-border);
            display: flex;
            justify-content: center;
            align-items: center;
            background: rgba(255, 255, 255, 0.6);
            backdrop-filter: blur(4px);
            -webkit-backdrop-filter: blur(4px);
            transition: all 0.2s;
            font-family: var(--font-main);
            z-index: 10;
            border-radius: 6px;
        }

        /* Enclosing cards around inputs matching ALU blocks */
        .input-group {
            position: absolute;
            background: rgba(230, 210, 240, 0.3);
            border: 2px solid rgba(0, 0, 0, 0.2);
            border-radius: 12px;
            backdrop-filter: blur(10px);
            -webkit-backdrop-filter: blur(10px);
            box-shadow: var(--glass-shadow);
            z-index: 1;
            display: flex;
            align-items: center;
        }

        .input-group-label {
            position: absolute;
            left: -80px;
            font-weight: bold;
            font-size: 1.2rem;
            color: var(--text-color);
            transform: rotate(-90deg);
            letter-spacing: 2px;
            text-transform: uppercase;
        }

        .group-a {
            position: absolute;
            left: 35px;
            width: 80px;
        }

        .group-b {
            position: absolute;
            left: 35px;
            width: 80px;
        }

        .group-s {
            bottom: -55px;
            left: 260px;
            width: 320px;
            height: 80px;
        }

        .group-s .input-group-label {
            left: -30px;
            top: 30px;
        }

        .io-value.active {
            background: #000;
            color: #fff;
        }

        /* Specific node positions */
        .in-cin {
            top: 30px;
            left: 50px;
        }

        /* A inputs base setup */
        .in-a3,
        .in-a2,
        .in-a1,
        .in-a0 {
            left: 50px;
        }

        /* B inputs base setup */
        .in-b3,
        .in-b2,
        .in-b1,
        .in-b0 {
            left: 50px;
        }

        /* Mode M */
        .in-m {
            bottom: -40px;
            left: 710px;
            flex-direction: column;
        }

        .mode-big-btn {
            width: 140px !important;
            height: 40px !important;
            font-size: 1rem !important;
            letter-spacing: 2px;
            background: #fff;
            color: #000;
        }

        .io-value.mode-big-btn.active {
            background: #000;
            color: #fff;
        }

        /* Select lines S */
        .in-s3 {
            bottom: -40px;
            left: 288px;
            flex-direction: column;
        }

        .in-s2 {
            bottom: -40px;
            left: 368px;
            flex-direction: column;
        }

        .in-s1 {
            bottom: -40px;
            left: 448px;
            flex-direction: column;
        }

        .in-s0 {
            bottom: -40px;
            left: 528px;
            flex-direction: column;
        }

        /* Output Register Box (horizontal, like Reg S) */
        .group-out {
            position: absolute;
            background: rgba(210, 235, 230, 0.3);
            border: 2px solid rgba(0, 0, 0, 0.2);
            border-radius: 12px;
            backdrop-filter: blur(10px);
            -webkit-backdrop-filter: blur(10px);
            box-shadow: var(--glass-shadow);
            z-index: 1;
            display: flex;
            align-items: center;
        }

        .group-out .input-group-label {
            position: absolute;
            bottom: -35px;
            left: 50%;
            transform: translateX(-50%);
            font-weight: bold;
            font-size: 1.2rem;
            color: var(--text-color);
            letter-spacing: 2px;
            text-transform: uppercase;
        }

        /* Output node positions (set dynamically via JS) */
        .out-f-node {
            flex-direction: column;
        }

        /* Displays Data */
        .hud {
            position: absolute;
            bottom: 20px;
            right: -260px;
            border: 1px solid rgba(0, 0, 0, 0.2);
            padding: 20px 22px;
            background: rgba(255, 255, 255, 0.35);
            backdrop-filter: blur(14px);
            -webkit-backdrop-filter: blur(14px);
            border-radius: 12px;
            width: 240px;
            z-index: 20;
            box-shadow: var(--glass-shadow);
            font-size: 1.3rem;
            /* Scaled up */
        }

        .hud-title {
            font-weight: bold;
            border-bottom: 1px solid #000;
            margin-bottom: 15px;
            padding-bottom: 5px;
            text-align: center;
            font-size: 1.5rem;
            /* Scaled up */
        }

        .hud-row {
            display: flex;
            justify-content: space-between;
            margin-bottom: 10px;
            /* More breathing room */
        }

        .equation {
            font-style: italic;
            text-align: center;
            margin-top: 15px;
            font-size: 1.4rem;
            /* Scaled up */
            border-top: 1px dashed #000;
            padding-top: 10px;
        }

        /* Highlight animating lines */
        path.pulse {
            stroke-width: 2.5;
            stroke-dasharray: 5, 5;
            animation: dash 1s linear infinite;
        }

        @keyframes dash {
            to {
                stroke-dashoffset: -10;
            }
        }

        /* Custom marker arrowhead definition hidden from view */
        svg {
            position: absolute;
        }

        /* Titles and Credits */
        .page-header {
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            height: 70px;
            display: flex;
            align-items: center;
            justify-content: center;
            background: rgba(255, 255, 255, 0.25);
            backdrop-filter: blur(24px);
            -webkit-backdrop-filter: blur(24px);
            border-bottom: 1px solid rgba(0, 0, 0, 0.15);
            font-size: 2rem;
            font-weight: bold;
            color: var(--text-color);
            letter-spacing: 5px;
            z-index: 100;
            box-shadow: 0 4px 30px rgba(0, 0, 0, 0.05);
        }

        .page-footer {
            position: absolute;
            bottom: 20px;
            width: 100%;
            text-align: center;
            font-size: 0.8rem;
            color: var(--text-color);
            letter-spacing: 2px;
            z-index: 100;
            opacity: 0.6;
        }
    </style>