document.addEventListener("DOMContentLoaded", function () {
        let lastScroll = 0;
        const threshold = window.innerHeight * 0.95;

        window.addEventListener("scroll", function () {
          const currentScroll = window.scrollY;

          // 切り替え
          if (currentScroll > threshold) {
            document.body.classList.add("scrolled");
          } else {
            document.body.classList.remove("scrolled");
          }

          // 上下判定
          if (currentScroll > lastScroll && currentScroll > 200) {
            document.body.classList.add("hide-header");
          } else {
            document.body.classList.remove("hide-header");
          }

          lastScroll = currentScroll;
        });
      });
      const hamburgers = document.querySelectorAll(".hamburger-overlay");
      const nav = document.querySelector(".nav-overlay");

      hamburgers.forEach((btn) => {
        btn.addEventListener("click", () => {
          hamburgers.forEach((b) => b.classList.toggle("active"));
          nav.classList.toggle("active");
          document.body.classList.toggle("menu-open");
        });
      });