之前看到有網站的游標長得像這樣，就一直很想用。這次花了些時間研究給弄好了。
游標

這個原理其實很簡單，用兩個 div，border-radius: 50%; 呈現圓形。CSS 套用樣式，JavaScript 讓他跟隨滑鼠就完成。

在程式和樣式部分我參考了這個：

See the Pen Circle Follow Cursor by Hakadao (@Hakadao) on CodePen.

這是我修改後的程式與樣式，讓他更搭配我的主題，也另外增加了一些顏色與形狀的變化：

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function getElementsWithTextNoLinksOrButtons() {
  return [...document.querySelectorAll("*")].filter(el => 
      el.textContent.trim() !== "" &&
      !el.closest("a") &&
      !el.closest("button") &&
      !el.querySelector("a") &&
      !el.querySelector("button") &&
      el.nodeType === Node.ELEMENT_NODE
  );
}

const cursor = document.querySelector("#cursor");
const cursorBorder = document.querySelector("#cursor-border");
const linksAndButtons = document.querySelectorAll("a, button");
const texts = getElementsWithTextNoLinksOrButtons();
const cursorPos = { x: 0, y: 0 };
const cursorBorderPos = { x: 0, y: 0 };

cursor.style.setProperty("--width", "10px");
cursor.style.setProperty("--height", "10px");

document.addEventListener("mousemove", (e) => {
  cursorPos.x = e.clientX;
  cursorPos.y = e.clientY;

  cursor.style.transform = `translate(${e.clientX}px, ${e.clientY}px)`;
});

document.addEventListener("mousedown", (e) => {
  cursor.style.setProperty("--width", `${cursor.style.getPropertyValue("--width").replace("px", "") * 1.8}px`);
  cursor.style.setProperty("--height", `${cursor.style.getPropertyValue("--height").replace("px", "") * 1.8}px`);
});

document.addEventListener("mouseup", (e) => {
  cursor.style.setProperty("--width", `${cursor.style.getPropertyValue("--width").replace("px", "") / 1.8}px`);
  cursor.style.setProperty("--height", `${cursor.style.getPropertyValue("--height").replace("px", "") / 1.8}px`);
});

texts.forEach((text) => {
  text.addEventListener("mouseover", (e) => {
    cursor.style.borderRadius = "0%";
    cursor.style.setProperty("--width", "2px");
    cursor.style.setProperty("--height", "20px");
  });
  text.addEventListener("mouseout", (e) => {
    cursor.style.borderRadius = "50%";
    cursor.style.setProperty("--width", "10px");
    cursor.style.setProperty("--height", "10px");
    

  });
});

linksAndButtons.forEach((linkAndButton) => {
  linkAndButton.addEventListener("mouseover", (e) => {
    cursor.style.backgroundColor = "#daaf61";
    cursorBorder.style.setProperty("--size", "50px");
  });
  linkAndButton.addEventListener("mouseout", (e) => {
    cursor.style.backgroundColor = "#95bcd6";
    cursorBorder.style.setProperty("--size", "28px");
  });
});

requestAnimationFrame(function loop() {
  const easting = 8;
  cursorBorderPos.x += (cursorPos.x - cursorBorderPos.x) / easting;
  cursorBorderPos.y += (cursorPos.y - cursorBorderPos.y) / easting;

  cursorBorder.style.transform = `translate(${cursorBorderPos.x}px, ${cursorBorderPos.y}px)`;
  requestAnimationFrame(loop);
});
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* {
    cursor: none;
}

/* 這段是專門對 butterfly 的，其他主題可能要自行修改 */
.search-dialog, .fancybox__container {
    *{cursor: auto;}
}

#cursor {
    position: fixed;
    top: calc(var(--height) / -2);
    left: calc(var(--width) / -2);
    width: var(--width);
    height: var(--height);
    background-color: #95bcd6;
    transition: top 0.15s ease-out, left 0.15s ease-out, width 0.15s ease-out, height 0.15s ease-out, background-color 0.15s ease-out;
    border-radius: 50%;
    pointer-events: none;
    z-index: 999;
}

#cursor-border {
    --size: 28px;
    position: fixed;
    top: calc(var(--size) / -2);
    left: calc(var(--size) / -2);
    width: var(--size);
    height: var(--size);
    border-radius: 50%;
    background-color:  #5c565156;
    mix-blend-mode: difference;
    pointer-events: none;
    transition: top 0.15s ease-out, left 0.15s ease-out, width 0.15s ease-out, height 0.15s ease-out, background-color 0.15s ease-out;
    z-index: 999;
}

把以上兩個檔案存在 source 資料夾下，並且在設定文件中的 Inject 加入下面這行就可以，記得路徑要填對。

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<div id="cursor-border"></div><div id="cursor"></div><link rel="stylesheet" href="/css/custom_cursor.css"><script src="/js/custom_cursor.js"></script>

當然其他不是 butterfly，而是其他網站或主題也可以用。

q(≧▽≦q)

20250707 更新

因為有人說我的網站太卡，所以我先把這個下架了。
（；´д｀）ゞ

20260225 更新

Vibe Coding 一下，請 AI 改善效能問題。不知道 AI 改的有沒有效，把程式放在下面並且重新使用游標。

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// ===== Cursor Elements =====
const cursor = document.querySelector("#cursor");
const cursorBorder = document.querySelector("#cursor-border");

if (!cursor || !cursorBorder) {
  console.warn("Custom cursor elements not found.");
}

// ===== State =====
const cursorPos = { x: 0, y: 0 };
const cursorBorderPos = { x: 0, y: 0 };
let currentState = "default"; // default | text | interactive

// ===== Initial Size =====
cursor.style.setProperty("--width", "10px");
cursor.style.setProperty("--height", "10px");

// ===== Helpers =====
function setDefaultCursor() {
  if (currentState === "default") return;
  currentState = "default";

  cursor.style.borderRadius = "50%";
  cursor.style.setProperty("--width", "10px");
  cursor.style.setProperty("--height", "10px");
  cursor.style.backgroundColor = "#95bcd6";
  cursorBorder.style.setProperty("--size", "28px");
}

function setTextCursor() {
  if (currentState === "text") return;
  currentState = "text";

  cursor.style.borderRadius = "0%";
  cursor.style.setProperty("--width", "2px");
  cursor.style.setProperty("--height", "20px");
  cursor.style.backgroundColor = "#95bcd6";
  cursorBorder.style.setProperty("--size", "28px");
}

function setInteractiveCursor() {
  if (currentState === "interactive") return;
  currentState = "interactive";

  cursor.style.borderRadius = "50%";
  cursor.style.setProperty("--width", "10px");
  cursor.style.setProperty("--height", "10px");
  cursor.style.backgroundColor = "#daaf61";
  cursorBorder.style.setProperty("--size", "50px");
}

// ===== Mouse Move =====
document.addEventListener("mousemove", (e) => {
  const x = e.clientX;
  const y = e.clientY;

  cursorPos.x = x;
  cursorPos.y = y;

  // Move small cursor (GPU friendly)
  cursor.style.transform = `translate3d(${x}px, ${y}px, 0)`;

  // Detect element under cursor
  const el = document.elementFromPoint(x, y);
  if (!el) return;

  // Interactive elements
  if (el.closest("a, button, [role='button'], input[type='button'], input[type='submit']")) {
    setInteractiveCursor();
    return;
  }

  // Text elements
  const textEl = el.closest(
    "p, span, h1, h2, h3, h4, h5, h6, li, strong, em, small, label"
  );

  if (textEl && textEl.textContent.trim() !== "") {
    setTextCursor();
  } else {
    setDefaultCursor();
  }
});

// ===== Click Effect =====
document.addEventListener("mousedown", () => {
  const w = parseFloat(getComputedStyle(cursor).getPropertyValue("--width")) || 10;
  const h = parseFloat(getComputedStyle(cursor).getPropertyValue("--height")) || 10;

  cursor.style.setProperty("--width", `${w * 1.8}px`);
  cursor.style.setProperty("--height", `${h * 1.8}px`);
});

document.addEventListener("mouseup", () => {
  const w = parseFloat(getComputedStyle(cursor).getPropertyValue("--width")) || 10;
  const h = parseFloat(getComputedStyle(cursor).getPropertyValue("--height")) || 10;

  cursor.style.setProperty("--width", `${w / 1.8}px`);
  cursor.style.setProperty("--height", `${h / 1.8}px`);
});

// ===== Smooth Border Follow =====
(function loop() {
  const easing = 8;

  cursorBorderPos.x += (cursorPos.x - cursorBorderPos.x) / easing;
  cursorBorderPos.y += (cursorPos.y - cursorBorderPos.y) / easing;

  cursorBorder.style.transform = `translate3d(${cursorBorderPos.x}px, ${cursorBorderPos.y}px, 0)`;

  requestAnimationFrame(loop);
})();