:root {
        --bg-color: #050505;
        --text-color: #fff;
      }

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

      body {
        background-color: var(--bg-color);
        color: var(--text-color);
        font-family: "Inter", "Noto Sans JP", "Helvetica Neue", "Arial",
          sans-serif;
        overflow-x: hidden;
      }

      section {
        min-height: 100vh;
        width: 100%;
        display: flex;
        flex-direction: column;
        align-items: center;
        justify-content: center;
        padding: 40px 20px;
        position: relative;
        border-bottom: 1px solid #333;
        z-index: 1;
      }

      h2 {
        font-size: 1.5rem;
        margin-bottom: 1rem;
        opacity: 0.9;
        font-weight: 700;
        text-align: center;
        z-index: 10;
        padding: 0.5em 1em;
        border-radius: 8px;
        backdrop-filter: blur(5px);
        letter-spacing: 0.05em;
      }

      .desc {
        margin-bottom: 2.5rem;
        color: #aaa;
        font-size: 0.9rem;
        text-align: center;
        z-index: 10;
        line-height: 1.8;
        letter-spacing: 0.02em;
      }

      /* =========================================
         Variation 1: CSS Variables Interpolation
         ========================================= */
      .demo-1-text {
        font-size: clamp(3rem, 10vw, 8rem);
        font-weight: 900;
        --c1: #dafa30;
        --c2: #f4a52d;
        /* 文字グラデーション */
        background-image: linear-gradient(90deg, var(--c1), var(--c2));
        background-clip: text;
        -webkit-background-clip: text;
        color: transparent;
        line-height: 1.1;
        text-align: center;
        letter-spacing: -0.02em;
      }

      /* =========================================
         Variation 2: Flowing Gradient
         ========================================= */
      .demo-2-box {
        width: 100%;
        max-width: 700px;
        height: 400px;
        border-radius: 30px;
        /* 色数を増やし、彩度を上げたグラデーション */
        background: linear-gradient(
          120deg,
          #ff00cc,
          #3333ff,
          #00ccff,
          #00ff99,
          #ffff00,
          #ff0000
        );
        background-size: 300% 300%;
        box-shadow: 0 20px 60px rgba(0, 204, 255, 0.4);
        display: flex;
        align-items: center;
        justify-content: center;
        font-size: 2.5rem;
        font-weight: 900;
        color: rgba(255, 255, 255, 1);
        text-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
      }

      /* =========================================
         Variation 3: Mouse Interaction Spotlight
         ========================================= */
      .demo-3-container {
        position: relative;
        width: 100%;
        max-width: 800px;
        padding: 3px;
        border-radius: 16px;
        overflow: hidden;
        background: #333;
        box-shadow: 0 10px 40px rgba(0, 0, 0, 0.5);
      }
      .demo-3-glow {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        /* 光の範囲を大きく、中心を明るく */
        background: radial-gradient(
          800px circle at var(--x, 50%) var(--y, 50%),
          rgba(255, 255, 255, 0.9),
          rgba(255, 255, 255, 0.1) 40%,
          transparent 60%
        );
        opacity: 0;
        transition: opacity 0.2s;
        pointer-events: none;
        z-index: 1;
      }
      .demo-3-container:hover .demo-3-glow {
        opacity: 1;
      }
      .demo-3-content {
        position: relative;
        background: #111; /* コントラスト比を高める */
        padding: 4rem 2rem;
        border-radius: 13px;
        z-index: 2;
        text-align: center;
      }
      .demo-3-content h3 {
        font-size: 2.5rem;
        font-weight: 700;
        background: linear-gradient(to right, #fff, #888);
        background-clip: text;
        -webkit-background-clip: text;
        color: transparent;
        letter-spacing: 0.02em;
      }

      /* =========================================
         Variation 4: Scroll Triggered Hue Rotate
         ========================================= */
      .demo-4-text {
        font-size: clamp(4rem, 12vw, 10rem);
        font-weight: 900; /* Extra Bold */
        color: transparent;
        -webkit-text-stroke: 2px rgba(255, 255, 255, 0.3);
        position: relative;
        white-space: nowrap;
        --bg-y: 0%;
        letter-spacing: -0.03em;
      }
      .demo-4-text::after {
        content: attr(data-text);
        position: absolute;
        left: 0;
        top: 0;
        width: 100%;
        height: 100%;
        /* レインボーをより鮮やかに */
        background-image: linear-gradient(
          180deg,
          #ff0000,
          #ff8800,
          #ffff00,
          #00ff00,
          #00ffff,
          #0000ff,
          #ff00ff,
          #ff0000
        );
        background-size: 100% 200%; /* 変化の幅を調整 */
        background-clip: text;
        -webkit-background-clip: text;
        color: transparent;
        -webkit-text-stroke: 0;
        background-position: 50% var(--bg-y);
        filter: drop-shadow(
          0 0 10px rgba(255, 255, 255, 0.3)
        ); /* 発光感を追加 */
      }

      /* =========================================
         Variation 5: Conic Gradient Border
         ========================================= */
      .demo-5-card {
        position: relative;
        width: 320px;
        height: 420px;
        background: #1a1a1a;
        border-radius: 24px;
        display: flex;
        flex-direction: column;
        align-items: center;
        justify-content: center;
        overflow: hidden;
        z-index: 1;
        box-shadow: 0 0 50px rgba(0, 255, 153, 0.2);

        --angle: 0deg;
      }

      .demo-5-card::before {
        content: "";
        position: absolute;
        top: -50%;
        left: -50%;
        width: 200%;
        height: 200%;

        /* ネオンカラーを強化 */
        background: conic-gradient(
          from var(--angle),
          transparent 0%,
          #00ccff 20%,
          #00ff99 50%,
          #ffff00 70%,
          transparent 80%
        );

        z-index: -1;
        /* 光の滲みを追加 */
        filter: blur(10px);
        opacity: 0.8;
      }

      /* シャープな線用のレイヤーを追加 */
      .demo-5-card .sharp-border {
        position: absolute;
        top: -50%;
        left: -50%;
        width: 200%;
        height: 200%;
        background: conic-gradient(
          from var(--angle),
          transparent 0%,
          #00ccff 20%,
          #00ff99 50%,
          #ffff00 70%,
          transparent 80%
        );
        z-index: -1;
      }

      .demo-5-card::after {
        content: "";
        position: absolute;
        inset: 6px; /* 境界線を太く */
        background: #111;
        border-radius: 18px;
        z-index: -1;
      }

      .demo-5-content {
        text-align: center;
        padding: 20px;
      }

      .demo-5-content h3 {
        font-family: "Inter", sans-serif;
        font-weight: 700;
        letter-spacing: 0.05em;
      }

      /* =========================================
         Variation 6: Blurry Mesh Gradient
         ========================================= */
      #section6 {
        overflow: hidden;
        background: #000;
        position: relative;
      }

      .mesh-container {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        /* ブラーを強めてより「オーロラ」っぽく */
        filter: blur(100px);
        z-index: 0;
        opacity: 0.8;
      }

      .mesh-blob {
        position: absolute;
        border-radius: 50%;
        mix-blend-mode: screen; /* 色を重ねて明るくする */
      }

      /* Blobの色とサイズを派手に */
      .blob-1 {
        width: 70vw;
        height: 70vw;
        background: #6a00ff;
        top: -20%;
        left: -20%;
      }

      .blob-2 {
        width: 60vw;
        height: 60vw;
        background: #ff0055;
        bottom: -20%;
        right: -20%;
      }

      .blob-3 {
        width: 50vw;
        height: 50vw;
        background: #00ffaa;
        top: 30%;
        left: 30%;
      }

      .blob-4 {
        width: 40vw;
        height: 40vw;
        background: #ffee00;
        bottom: 10%;
        left: 10%;
      }