{"id":18162,"date":"2026-07-15T06:20:05","date_gmt":"2026-07-15T06:20:05","guid":{"rendered":"https:\/\/withcode.tech\/media\/?p=18162"},"modified":"2026-07-21T11:37:47","modified_gmt":"2026-07-21T11:37:47","slug":"css-z-index","status":"publish","type":"post","link":"https:\/\/withcode.tech\/media\/css-z-index\/","title":{"rendered":"\u30102026\u5e74\u7248\u3011CSS z-index\u306e\u4f7f\u3044\u65b9\u5b8c\u5168\u30ac\u30a4\u30c9\uff5c\u91cd\u306a\u308a\u9806\u30fb\u52b9\u304b\u306a\u3044\u539f\u56e0\u30fb\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8"},"content":{"rendered":"<p class=\"wp-block-paragraph\">\u300cz-index\u3092999\u306b\u3057\u305f\u306e\u306b\u3001\u8981\u7d20\u304c\u5f8c\u308d\u306b\u96a0\u308c\u305f\u307e\u307e\u300d\u300c\u30e2\u30fc\u30c0\u30eb\u304c\u30d8\u30c3\u30c0\u30fc\u306e\u4e0b\u306b\u6f5c\u308a\u8fbc\u3093\u3067\u3057\u307e\u3046\u300d\u2014\u2014CSS\u306ez-index\u306f\u3001\u3053\u3046\u3057\u305f\u91cd\u306a\u308a\u9806\u306e\u30c8\u30e9\u30d6\u30eb\u3067\u6700\u3082\u983b\u7e41\u306b\u767b\u5834\u3059\u308b\u30d7\u30ed\u30d1\u30c6\u30a3\u306e\u3072\u3068\u3064\u3067\u3059\u3002\u6570\u5024\u3092\u5927\u304d\u304f\u3059\u308c\u3070\u89e3\u6c7a\u3059\u308b\u3068\u601d\u3044\u304d\u3084\u3001\u307e\u3063\u305f\u304f\u52b9\u679c\u304c\u306a\u3044\u30b1\u30fc\u30b9\u3082\u591a\u304f\u3001\u539f\u56e0\u304c\u3064\u304b\u3081\u305a\u306b\u8a66\u884c\u932f\u8aa4\u3092\u7e70\u308a\u8fd4\u3057\u305f\u7d4c\u9a13\u306e\u3042\u308b\u65b9\u3082\u591a\u3044\u3067\u3057\u3087\u3046\u3002<\/p>\n\n\n<p class=\"wp-block-paragraph\">z-index\u304c\u601d\u3044\u901a\u308a\u306b\u52d5\u304b\u306a\u3044\u6839\u672c\u7684\u306a\u7406\u7531\u306f\u3001<strong>\u300c\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\uff08\u91cd\u306a\u308a\u6587\u8108\uff09\u300d<\/strong>\u3068\u3044\u3046\u6982\u5ff5\u3092\u7406\u89e3\u3057\u3066\u3044\u306a\u3044\u3053\u3068\u306b\u3042\u308a\u307e\u3059\u3002\u3053\u306e\u30ac\u30a4\u30c9\u3067\u306f\u3001z-index\u306e\u57fa\u672c\u304b\u3089\u3001position\u6307\u5b9a\u3068\u306e\u95a2\u4fc2\u3001\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u306e\u4ed5\u7d44\u307f\u3001\u52b9\u304b\u306a\u3044\u3068\u304d\u306e\u539f\u56e0\u3068\u5bfe\u51e6\u3001\u305d\u3057\u3066\u56fa\u5b9a\u30d8\u30c3\u30c0\u30fc\u30fb\u30c9\u30ed\u30c3\u30d7\u30c0\u30a6\u30f3\u30fb\u30e2\u30fc\u30c0\u30eb\u3068\u3044\u3063\u305f\u5b9f\u8df5\u30b7\u30fc\u30f3\u3067\u306e\u6b63\u3057\u3044\u4f7f\u3044\u65b9\u307e\u3067\u3001\u30b3\u30d4\u30da\u3067\u52d5\u304f\u30b3\u30fc\u30c9\u4f8b\u3092\u4ea4\u3048\u306a\u304c\u3089\u9806\u3092\u8ffd\u3063\u3066\u89e3\u8aac\u3057\u307e\u3059\u3002<\/p>\n\n\n<p class=\"wp-block-paragraph\">\u521d\u5fc3\u8005\u306e\u65b9\u306fz-index\u306e\u57fa\u790e\u304b\u3089\u3001\u4e2d\u7d1a\u8005\u306e\u65b9\u306f\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3084\u7ba1\u7406\u8853\u306e\u30bb\u30af\u30b7\u30e7\u30f3\u304b\u3089\u8aad\u307f\u59cb\u3081\u308b\u3068\u52b9\u679c\u7684\u3067\u3059\u3002\u3053\u306e\u30ac\u30a4\u30c9\u3092\u8aad\u307f\u7d42\u3048\u305f\u5f8c\u306b\u306f\u3001z-index\u3067\u8a70\u307e\u308b\u3053\u3068\u304c\u307b\u307c\u306a\u304f\u306a\u308b\u306f\u305a\u3067\u3059\u3002<\/p>\n\n\n<h2 class=\"wp-block-heading\">z-index\u3068\u306f\u4f55\u304b\u2014\u2014\u57fa\u672c\u3068\u5f79\u5272<\/h2>\n\n\n<h3 class=\"wp-block-heading\">\u753b\u9762\u5965\u884c\u304d\u65b9\u5411\uff08Z\u8ef8\uff09\u3092\u64cd\u308b\u30d7\u30ed\u30d1\u30c6\u30a3<\/h3>\n\n\n<p class=\"wp-block-paragraph\">CSS\u306e\u30ec\u30a4\u30a2\u30a6\u30c8\u306f\u3001X\u8ef8\uff08\u6a2a\uff09\u30fbY\u8ef8\uff08\u7e26\uff09\u306e2\u6b21\u5143\u5e73\u9762\u306b\u52a0\u3048\u3066\u3001<strong>Z\u8ef8\uff08\u753b\u9762\u306e\u5965\u884c\u304d\u65b9\u5411\uff09<\/strong>\u3068\u3044\u3046\u6982\u5ff5\u3092\u6301\u3063\u3066\u3044\u307e\u3059\u3002z-index\u306f\u3001\u3053\u306e\u5965\u884c\u304d\u65b9\u5411\u306b\u304a\u3051\u308b\u8981\u7d20\u306e\u91cd\u306a\u308a\u9806\u3092\u5236\u5fa1\u3059\u308b\u30d7\u30ed\u30d1\u30c6\u30a3\u3067\u3059\u3002\u5024\u304c\u5927\u304d\u3044\u307b\u3069\u624b\u524d\uff08\u30e6\u30fc\u30b6\u30fc\u5074\uff09\u306b\u8868\u793a\u3055\u308c\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>\/* z-index\u306e\u57fa\u672c\u7684\u306a\u66f8\u304d\u65b9 *\/\n.element {\n  position: relative; \/* position\u6307\u5b9a\u304c\u5fc5\u9808 *\/\n  z-index: 10;        \/* \u6574\u6570\u5024\uff08\u8ca0\u306e\u5024\u3082\u53ef\uff09 *\/\n}\n<\/code><\/pre><\/div>\n\n\n<h3 class=\"wp-block-heading\">\u6307\u5b9a\u3067\u304d\u308b\u5024\u306e\u7a2e\u985e<\/h3>\n\n<ul class=\"wp-block-list\">\n<li><strong>\u6574\u6570\u5024\uff08\u6b63\uff09<\/strong>: z-index: 1\u3001z-index: 100 \u306a\u3069\u3002\u5024\u304c\u5927\u304d\u3044\u307b\u3069\u524d\u9762\u3002<\/li>\n<li><strong>\u6574\u6570\u5024\uff08\u8ca0\uff09<\/strong>: z-index: -1 \u306a\u3069\u3002\u901a\u5e38\u306e\u6587\u66f8\u30d5\u30ed\u30fc\u3088\u308a\u5f8c\u308d\u306b\u914d\u7f6e\u3002<\/li>\n<li><strong>auto\uff08\u521d\u671f\u5024\uff09<\/strong>: \u89aa\u306e\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u304b\u3089\u5024\u3092\u7d99\u627f\u3057\u305f\u6271\u3044\u306b\u306a\u308a\u3001\u65b0\u3057\u3044\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3092\u4f5c\u3089\u306a\u3044\u3002<\/li>\n<\/ul>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>.box-front {\n  position: absolute;\n  z-index: 2; \/* \u624b\u524d\u306b\u8868\u793a *\/\n}\n\n.box-back {\n  position: absolute;\n  z-index: 1; \/* \u5965\u306b\u8868\u793a *\/\n}\n\n.box-behind-all {\n  position: relative;\n  z-index: -1; \/* \u6587\u66f8\u30d5\u30ed\u30fc\u3088\u308a\u5965 *\/\n}\n<\/code><\/pre><\/div>\n\n\n<h2 class=\"wp-block-heading\">position\u6307\u5b9a\u304c\u306a\u3044\u3068z-index\u306f\u52b9\u304b\u306a\u3044<\/h2>\n\n\n<h3 class=\"wp-block-heading\">\u306a\u305cposition\u304c\u5fc5\u8981\u306a\u306e\u304b<\/h3>\n\n<p class=\"wp-block-paragraph\">z-index\u304c\u6700\u3082\u3088\u304f\u5f15\u3063\u304b\u304b\u308b\u843d\u3068\u3057\u7a74\u304c\u3001<strong>position: static\uff08\u521d\u671f\u5024\uff09\u306e\u8981\u7d20\u306b\u306fz-index\u304c\u9069\u7528\u3055\u308c\u306a\u3044<\/strong>\u3068\u3044\u3046\u4ed5\u69d8\u3067\u3059\u3002CSS\u306e\u4ed5\u69d8\u4e0a\u3001z-index\u30d7\u30ed\u30d1\u30c6\u30a3\u304c\u6709\u52b9\u306b\u306a\u308b\u306e\u306f\u300c\u914d\u7f6e\u8981\u7d20\uff08positioned element\uff09\u300d\u2014\u2014\u3064\u307e\u308a position \u304c relative \/ absolute \/ fixed \/ sticky \u306e\u3044\u305a\u308c\u304b\u306b\u8a2d\u5b9a\u3055\u308c\u305f\u8981\u7d20\u306e\u307f\u3067\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>\/* NG: static\u306e\u307e\u307e\u3067\u306fz-index\u306f\u7121\u8996\u3055\u308c\u308b *\/\n.bad-example {\n  \/* position: static; \u2190 \u30c7\u30d5\u30a9\u30eb\u30c8\u306e\u307e\u307e *\/\n  z-index: 9999; \/* \u52b9\u304b\u306a\u3044 *\/\n}\n\n\/* OK: position\u3092\u6307\u5b9a\u3059\u308b\u3068\u6709\u52b9\u306b\u306a\u308b *\/\n.good-example {\n  position: relative; \/* \u307e\u305f\u306f absolute \/ fixed \/ sticky *\/\n  z-index: 9999;      \/* \u6b63\u3057\u304f\u52b9\u304f *\/\n}\n<\/code><\/pre><\/div>\n\n<p class=\"wp-block-paragraph\">position: relative \u306f\u30ec\u30a4\u30a2\u30a6\u30c8\u3078\u306e\u5f71\u97ff\u304c\u6700\u5c0f\u9650\u3067\u6e08\u3080\u305f\u3081\u3001\u300c\u91cd\u306a\u308a\u9806\u3092\u5236\u5fa1\u3057\u305f\u3044\u3051\u308c\u3069\u4f4d\u7f6e\u306f\u305a\u3089\u3057\u305f\u304f\u306a\u3044\u300d\u3068\u3044\u3046\u5834\u9762\u3067\u6700\u3082\u3088\u304f\u4f7f\u308f\u308c\u307e\u3059\u3002top \/ left \u306a\u3069\u306e\u30aa\u30d5\u30bb\u30c3\u30c8\u3092\u6307\u5b9a\u3057\u306a\u3051\u308c\u3070\u3001\u898b\u305f\u76ee\u4e0a\u306e\u4f4d\u7f6e\u306f\u5909\u308f\u308a\u307e\u305b\u3093\u3002<\/p>\n\n\n<h3 class=\"wp-block-heading\">positon\u3068z-index\u306e\u5bfe\u5fdc\u8868<\/h3>\n\n<ul class=\"wp-block-list\">\n<li><strong>static<\/strong>: z-index\u306f\u7121\u52b9\uff08\u521d\u671f\u5024\uff09<\/li>\n<li><strong>relative<\/strong>: z-index\u304c\u6709\u52b9\u3002\u5143\u306e\u4f4d\u7f6e\u304b\u3089\u76f8\u5bfe\u7684\u306b\u305a\u3089\u305b\u308b<\/li>\n<li><strong>absolute<\/strong>: z-index\u304c\u6709\u52b9\u3002\u76f4\u8fd1\u306e\u914d\u7f6e\u7956\u5148\u3092\u57fa\u6e96\u306b\u914d\u7f6e<\/li>\n<li><strong>fixed<\/strong>: z-index\u304c\u6709\u52b9\u3002\u30d3\u30e5\u30fc\u30dd\u30fc\u30c8\u3092\u57fa\u6e96\u306b\u56fa\u5b9a\u914d\u7f6e<\/li>\n<li><strong>sticky<\/strong>: z-index\u304c\u6709\u52b9\u3002\u30b9\u30af\u30ed\u30fc\u30eb\u306b\u5fdc\u3058\u3066static\u3068fixed\u3092\u5207\u308a\u66ff\u3048<\/li>\n<\/ul>\n\n\n<h2 class=\"wp-block-heading\">\u91cd\u306a\u308a\u9806\u306e\u57fa\u672c\u30eb\u30fc\u30eb\u2014\u2014HTML\u306e\u9806\u5e8f\u3068\u306e\u95a2\u4fc2<\/h2>\n\n\n<h3 class=\"wp-block-heading\">z-index\u304c\u540c\u3058\uff08\u307e\u305f\u306fauto\uff09\u306e\u5834\u5408\u306fHTML\u306e\u5f8c\u308d\u304c\u4e0a<\/h3>\n\n<p class=\"wp-block-paragraph\">z-index\u3092\u660e\u793a\u7684\u306b\u6307\u5b9a\u3057\u306a\u3044\u5834\u5408\u3001\u307e\u305f\u306f\u540c\u3058\u5024\u306e\u5834\u5408\u306f\u3001<strong>HTML\u30bd\u30fc\u30b9\u4e0a\u3067\u5f8c\u306b\u8a18\u8ff0\u3055\u308c\u305f\u8981\u7d20\u304c\u624b\u524d\u306b\u8868\u793a\u3055\u308c\u307e\u3059<\/strong>\u3002\u3053\u308c\u3092\u300c\u5f8c\u5165\u308c\u512a\u5148\uff08later in the DOM wins\uff09\u300d\u306e\u30eb\u30fc\u30eb\u3068\u547c\u3073\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-markup\" data-lang=\"HTML\"><code>&lt;div class=\"box box-1\"&gt;BOX 1&lt;\/div&gt;\n&lt;div class=\"box box-2\"&gt;BOX 2\uff08\u3053\u3061\u3089\u304c\u524d\u9762\uff09&lt;\/div&gt;\n<\/code><\/pre><\/div>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>.box {\n  width: 200px;\n  height: 200px;\n  position: absolute;\n}\n\n.box-1 {\n  background: #d16176;\n  top: 0;\n  left: 0;\n}\n\n.box-2 {\n  background: #51322b;\n  top: 50px;\n  left: 50px;\n  \/* z-index\u306a\u3057\u2192 HTML\u3067\u5f8c\u306e.box-2\u304c\u524d\u9762\u306b\u6765\u308b *\/\n}\n<\/code><\/pre><\/div>\n\n<p class=\"wp-block-paragraph\">\u4e0a\u8a18\u306e\u30b3\u30fc\u30c9\u3067\u306f .box-2 \u304c .box-1 \u306e\u4e0a\u306b\u91cd\u306a\u308a\u307e\u3059\u3002\u3053\u308c\u306fz-index\u3092\u4f7f\u308f\u306a\u304f\u3066\u3082\u6210\u7acb\u3059\u308b\u57fa\u672c\u30eb\u30fc\u30eb\u3067\u3059\u3002<\/p>\n\n\n<h3 class=\"wp-block-heading\">z-index\u306b\u3088\u308b\u4e0a\u66f8\u304d<\/h3>\n\n<p class=\"wp-block-paragraph\">HTML\u306e\u9806\u5e8f\u306b\u95a2\u4fc2\u306a\u304f\u524d\u9762\u306b\u6301\u3063\u3066\u304d\u305f\u3044\u5834\u5408\u306b\u3001z-index\u3067\u660e\u793a\u7684\u306a\u5024\u3092\u4e0e\u3048\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>.box-1 {\n  position: relative;\n  z-index: 2; \/* HTML\u3067\u306f\u5148\u3060\u304c\u3001z-index\u3067\u524d\u9762\u306b *\/\n}\n\n.box-2 {\n  position: relative;\n  z-index: 1; \/* HTML\u3067\u306f\u5f8c\u3060\u304c\u3001z-index\u3067\u80cc\u9762\u306b *\/\n}\n<\/code><\/pre><\/div>\n\n\n<h2 class=\"wp-block-heading\">\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\uff08\u91cd\u306a\u308a\u6587\u8108\uff09\u306e\u4ed5\u7d44\u307f<\/h2>\n\n\n<h3 class=\"wp-block-heading\">\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3068\u306f\u4f55\u304b<\/h3>\n\n<p class=\"wp-block-paragraph\">z-index\u3092\u7406\u89e3\u3059\u308b\u4e0a\u3067\u6700\u3082\u91cd\u8981\u306a\u6982\u5ff5\u304c<strong>\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\uff08Stacking Context\u30fb\u91cd\u306a\u308a\u6587\u8108\uff09<\/strong>\u3067\u3059\u3002\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3068\u306f\u3001\u300c\u305d\u306e\u5185\u90e8\u306e\u8981\u7d20\u306e\u91cd\u306a\u308a\u9806\u304c\u3001\u5916\u90e8\u306e\u8981\u7d20\u306b\u5bfe\u3057\u3066\u72ec\u7acb\u3057\u305f\u30b0\u30eb\u30fc\u30d7\u300d\u3092\u6307\u3057\u307e\u3059\u3002<\/p>\n\n<p class=\"wp-block-paragraph\">\u305f\u3068\u3048\u308b\u306a\u3089\u3001\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u306f\u300c\u900f\u660e\u306a\u30c8\u30ec\u30a4\u300d\u306e\u3088\u3046\u306a\u3082\u306e\u3067\u3059\u3002\u30c8\u30ec\u30a4\u306e\u4e2d\u306e\u8981\u7d20\u306f\u30c8\u30ec\u30a4\u5185\u3067z-index\u3092\u7af6\u3044\u5408\u3044\u307e\u3059\u304c\u3001\u5225\u306e\u30c8\u30ec\u30a4\u306e\u8981\u7d20\u3068\u306f\u76f4\u63a5\u7af6\u4e89\u3057\u307e\u305b\u3093\u3002\u30c8\u30ec\u30a4\u81ea\u4f53\u306ez-index\u304c\u3001\u4ed6\u306e\u30c8\u30ec\u30a4\u3084\u8981\u7d20\u3068\u306e\u76f8\u5bfe\u7684\u306a\u91cd\u306a\u308a\u9806\u3092\u6c7a\u3081\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-markup\" data-lang=\"HTML\"><code>&lt;!-- ParentA\u304c\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3092\u5f62\u6210 --&gt;\n&lt;div class=\"parent-a\"&gt; &lt;!-- z-index: 1 --&gt;\n  &lt;div class=\"child-a\"&gt;&lt;\/div&gt; &lt;!-- z-index: 9999 \u3067\u3082\u89aa\u306e\u5916\u306b\u306f\u51fa\u3089\u308c\u306a\u3044 --&gt;\n&lt;\/div&gt;\n\n&lt;!-- ParentB\u304c\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3092\u5f62\u6210 --&gt;\n&lt;div class=\"parent-b\"&gt; &lt;!-- z-index: 2 --&gt;\n  &lt;div class=\"child-b\"&gt;&lt;\/div&gt; &lt;!-- z-index: 1 \u3067\u3082parent-a\u3088\u308a\u524d\u9762 --&gt;\n&lt;\/div&gt;\n<\/code><\/pre><\/div>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>.parent-a {\n  position: relative;\n  z-index: 1; \/* \u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u5f62\u6210 *\/\n}\n\n.child-a {\n  position: relative;\n  z-index: 9999; \/* parent-a\u306e\u4e2d\u3067\u306e\u9806\u4f4d\u3002parent-b\u81ea\u4f53\u306b\u306f\u52dd\u3066\u306a\u3044 *\/\n}\n\n.parent-b {\n  position: relative;\n  z-index: 2; \/* parent-a\u3088\u308a\u5927\u304d\u3044\u306e\u3067\u3001parent-b\u5168\u4f53\u304c\u524d\u9762\u306b *\/\n}\n\n.child-b {\n  position: relative;\n  z-index: 1;\n}\n<\/code><\/pre><\/div>\n\n<p class=\"wp-block-paragraph\">\u7d50\u679c\u3068\u3057\u3066\u3001child-a\uff08z-index: 9999\uff09\u3088\u308a\u3082 child-b\uff08z-index: 1\uff09\u306e\u65b9\u304c\u524d\u9762\u306b\u8868\u793a\u3055\u308c\u307e\u3059\u3002\u3053\u308c\u304c\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u306e\u672c\u8cea\u3067\u3059\u3002<\/p>\n\n\n<h3 class=\"wp-block-heading\">\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u304c\u4f5c\u3089\u308c\u308b\u6761\u4ef6<\/h3>\n\n<p class=\"wp-block-paragraph\">\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u306f\u3001\u4ee5\u4e0b\u306e\u6761\u4ef6\u306e\u3044\u305a\u308c\u304b\u3092\u6e80\u305f\u3057\u305f\u8981\u7d20\u306b\u81ea\u52d5\u7684\u306b\u4f5c\u3089\u308c\u307e\u3059\u3002<\/p>\n\n<ul class=\"wp-block-list\">\n<li>\u30eb\u30fc\u30c8\u8981\u7d20\uff08&lt;html&gt;\uff09<\/li>\n<li>position \u304c relative \/ absolute \/ fixed \/ sticky \u304b\u3064 z-index \u304c auto \u4ee5\u5916\u306e\u6574\u6570\u5024\u3092\u6301\u3064\u8981\u7d20<\/li>\n<li>opacity \u304c 1 \u672a\u6e80\u306e\u8981\u7d20<\/li>\n<li>transform \u304c none \u4ee5\u5916\u306e\u8981\u7d20<\/li>\n<li>filter \u304c none \u4ee5\u5916\u306e\u8981\u7d20<\/li>\n<li>will-change \u306b opacity \/ transform \/ filter \u306e\u3044\u305a\u308c\u304b\u3092\u6307\u5b9a\u3057\u305f\u8981\u7d20<\/li>\n<li>isolation: isolate \u3092\u6307\u5b9a\u3057\u305f\u8981\u7d20<\/li>\n<li>mix-blend-mode \u304c normal \u4ee5\u5916\u306e\u8981\u7d20<\/li>\n<li>contain \u306b layout \/ paint \/ strict \/ content \u3092\u542b\u3080\u8981\u7d20<\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">\u3053\u306e\u30ea\u30b9\u30c8\u306e\u4e2d\u3067\u7279\u306b\u898b\u843d\u3068\u3057\u3084\u3059\u3044\u306e\u304c\u3001<strong>opacity \/ transform \/ filter<\/strong>\u3067\u3059\u3002\u6b21\u306e\u30bb\u30af\u30b7\u30e7\u30f3\u3067\u8a73\u3057\u304f\u6398\u308a\u4e0b\u3052\u307e\u3059\u3002<\/p>\n\n\n<h2 class=\"wp-block-heading\">z-index\u304c\u52b9\u304b\u306a\u30445\u3064\u306e\u539f\u56e0\u3068\u5bfe\u51e6\u6cd5<\/h2>\n\n\n<h3 class=\"wp-block-heading\">\u539f\u56e01: position\u304c\u6307\u5b9a\u3055\u308c\u3066\u3044\u306a\u3044<\/h3>\n\n<p class=\"wp-block-paragraph\">\u6700\u3082\u591a\u3044\u539f\u56e0\u3067\u3059\u3002\u524d\u8ff0\u306e\u901a\u308a\u3001position: static \u306e\u307e\u307e\u3067\u306fz-index\u306f\u7121\u8996\u3055\u308c\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>\/* \u76f4\u3057\u65b9: position\u3092\u8ffd\u52a0\u3059\u308b *\/\n.element {\n  position: relative; \/* \u3053\u308c\u3092\u8ffd\u52a0\u3059\u308b\u3060\u3051\u3067\u89e3\u6c7a\u3059\u308b\u3053\u3068\u304c\u591a\u3044 *\/\n  z-index: 10;\n}\n<\/code><\/pre><\/div>\n\n\n<h3 class=\"wp-block-heading\">\u539f\u56e02: \u89aa\u8981\u7d20\u304c\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3092\u5f62\u6210\u3057\u3066\u3044\u308b<\/h3>\n\n<p class=\"wp-block-paragraph\">\u5b50\u8981\u7d20\u306b\u3069\u308c\u3060\u3051\u5927\u304d\u306az-index\u3092\u6307\u5b9a\u3057\u3066\u3082\u3001\u89aa\u306e\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u306e\u300c\u5916\u300d\u306b\u306f\u51fa\u3089\u308c\u307e\u305b\u3093\u3002\u30e2\u30fc\u30c0\u30eb\u304c\u7279\u5b9a\u306e\u8981\u7d20\u306e\u4e0b\u306b\u96a0\u308c\u3066\u3057\u307e\u3046\u30b1\u30fc\u30b9\u306e\u591a\u304f\u304c\u3053\u308c\u3067\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>\/* \u554f\u984c\u306e\u3042\u308b\u30b1\u30fc\u30b9 *\/\n.parent {\n  position: relative;\n  z-index: 1; \/* \u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3092\u5f62\u6210\u3057\u3066\u3057\u307e\u3063\u3066\u3044\u308b *\/\n  transform: translateZ(0); \/* \u3053\u308c\u3082\u5f62\u6210\u3059\u308b *\/\n}\n\n.modal {\n  position: fixed;\n  z-index: 9999; \/* \u89aa\u306e\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u306b\u9589\u3058\u8fbc\u3081\u3089\u308c\u3001\u671f\u5f85\u901a\u308a\u306b\u52d5\u304b\u306a\u3044 *\/\n}\n<\/code><\/pre><\/div>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>\/* \u76f4\u3057\u65b91: \u89aa\u306ez-index\u3092auto\u306b\u3057\u3066\u5f62\u6210\u3092\u89e3\u9664 *\/\n.parent {\n  position: relative;\n  \/* z-index\u3092\u524a\u9664\u3001\u307e\u305f\u306fauto\u306b *\/\n}\n\n\/* \u76f4\u3057\u65b92: \u30e2\u30fc\u30c0\u30eb\u3092body\u76f4\u4e0b\u306b\u79fb\u52d5\uff08DOM\u69cb\u9020\u3092\u5909\u3048\u308b\uff09 *\/\n\/* HTML\u3067\u30e2\u30fc\u30c0\u30eb\u3092&lt;body&gt;\u306e\u76f4\u524d\u306e\u5b50\u8981\u7d20\u3068\u3057\u3066\u914d\u7f6e\u3059\u308b *\/\n<\/code><\/pre><\/div>\n\n\n<h3 class=\"wp-block-heading\">\u539f\u56e03: \u6bd4\u8f03\u5bfe\u8c61\u306e\u8981\u7d20\u304c\u5225\u306e\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u306b\u3044\u308b<\/h3>\n\n<p class=\"wp-block-paragraph\">A\u8981\u7d20\u3068B\u8981\u7d20\u306ez-index\u3092\u6bd4\u8f03\u3057\u305f\u3044\u306e\u306b\u3001\u305d\u308c\u305e\u308c\u304c\u5225\u306e\u89aa\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u306b\u5c5e\u3057\u3066\u3044\u308b\u5834\u5408\u3001z-index\u306e\u6570\u5024\u3067\u306f\u306a\u304f<strong>\u89aa\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u540c\u58eb\u306e\u91cd\u306a\u308a\u9806<\/strong>\u304c\u7d50\u679c\u3092\u6c7a\u3081\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>\/* \u76f4\u3057\u65b9: \u4e21\u8981\u7d20\u3092\u540c\u3058\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u306e\u5144\u5f1f\u306b\u3059\u308b *\/\n\/* HTML\u306e\u69cb\u9020\u3092\u898b\u76f4\u3057\u3001\u5171\u901a\u306e\u89aa\u306e\u76f4\u63a5\u306e\u5b50\u306b\u3059\u308b *\/\n\n.wrapper {\n  \/* \u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3092\u4f5c\u3089\u306a\u3044 *\/\n}\n\n.element-a {\n  position: relative;\n  z-index: 2;\n}\n\n.element-b {\n  position: relative;\n  z-index: 1;\n}\n<\/code><\/pre><\/div>\n\n\n<h3 class=\"wp-block-heading\">\u539f\u56e04: float\u3068\u306e\u7af6\u5408<\/h3>\n\n<p class=\"wp-block-paragraph\">\u53e4\u3044\u30b3\u30fc\u30c9\u3067\u306f float \u3092\u4f7f\u3063\u305f\u30ec\u30a4\u30a2\u30a6\u30c8\u306b z-index \u304c\u7d61\u3093\u3067\u610f\u56f3\u3057\u306a\u3044\u91cd\u306a\u308a\u304c\u8d77\u304d\u308b\u3053\u3068\u304c\u3042\u308a\u307e\u3059\u3002float\u3055\u308c\u305f\u8981\u7d20\u306f\u901a\u5e38\u30d5\u30ed\u30fc\u306e\u4e0a\u306b\u914d\u7f6e\u3055\u308c\u307e\u3059\u304c\u3001z-index\u306e\u7af6\u4e89\u306f\u914d\u7f6e\u7956\u5148\u3068\u6bd4\u3079\u3066\u5224\u5b9a\u3055\u308c\u307e\u3059\u3002\u30e2\u30c0\u30f3\u306aFlexbox\u30fbGrid\u3078\u306e\u79fb\u884c\u3067\u591a\u304f\u306f\u89e3\u6c7a\u3057\u307e\u3059\u3002<\/p>\n\n\n<h3 class=\"wp-block-heading\">\u539f\u56e05: DOM\u306e\u5916\u306b\u51fa\u308b\u3079\u304d\u8981\u7d20\u304c\u5185\u5074\u306b\u3044\u308b<\/h3>\n\n<p class=\"wp-block-paragraph\">position: fixed \u306e\u8981\u7d20\u306f\u300c\u30d3\u30e5\u30fc\u30dd\u30fc\u30c8\u3092\u57fa\u6e96\u306b\u56fa\u5b9a\u300d\u3055\u308c\u307e\u3059\u304c\u3001<strong>\u89aa\u306btransform\u3084filter\u304c\u304b\u304b\u3063\u3066\u3044\u308b\u3068\u305d\u306e\u89aa\u3092\u57fa\u6e96\u306b\u5909\u308f\u3063\u3066\u3057\u307e\u3046<\/strong>\u3068\u3044\u3046\u4ed5\u69d8\u304c\u3042\u308a\u307e\u3059\uff08\u5f8c\u8ff0\uff09\u3002\u3053\u306e\u5834\u5408\u3082DOM\u69cb\u9020\u306e\u898b\u76f4\u3057\u304c\u6839\u672c\u7684\u306a\u89e3\u6c7a\u7b56\u3067\u3059\u3002<\/p>\n\n\n<h2 class=\"wp-block-heading\">opacity \/ transform \/ filter \/ will-change\u304c\u4f5c\u308b\u300c\u610f\u56f3\u3057\u306a\u3044\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u300d<\/h2>\n\n\n<h3 class=\"wp-block-heading\">\u900f\u660e\u306b\u3057\u305f\u3060\u3051\u3067\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u304c\u751f\u307e\u308c\u308b<\/h3>\n\n<p class=\"wp-block-paragraph\">CSS\u30a2\u30cb\u30e1\u30fc\u30b7\u30e7\u30f3\u3084\u8996\u899a\u52b9\u679c\u3067\u3088\u304f\u4f7f\u3046opacity\u30fbtransform\u30fbfilter\u306f\u3001<strong>\u5024\u3092\u5909\u66f4\u3059\u308b\u3060\u3051\u3067\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3092\u751f\u6210\u3057\u307e\u3059<\/strong>\u3002\u3053\u308c\u3092\u77e5\u3089\u305a\u306b\u4f7f\u3046\u3068\u3001\u610f\u56f3\u3057\u306a\u3044\u91cd\u306a\u308a\u9806\u306e\u30d0\u30b0\u304c\u767a\u751f\u3057\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>\/* \u3053\u308c\u3089\u306f\u3059\u3079\u3066\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3092\u751f\u6210\u3059\u308b *\/\n\n.fade-in {\n  opacity: 0.99; \/* 1\u672a\u6e80\u306a\u30890.99\u3067\u3082\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u751f\u6210 *\/\n}\n\n.slide-in {\n  transform: translateX(0); \/* none\u3067\u306a\u3051\u308c\u3070\u751f\u6210 *\/\n}\n\n.blur-bg {\n  filter: blur(0px); \/* none\u3067\u306a\u3051\u308c\u3070\u751f\u6210 *\/\n}\n\n.gpu-hint {\n  will-change: transform; \/* transform\/opacity\/filter\u3092\u6307\u5b9a\u3059\u308b\u3068\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u751f\u6210 *\/\n}\n<\/code><\/pre><\/div>\n\n\n<h3 class=\"wp-block-heading\">transform\u3068position: fixed\u306e\u7d44\u307f\u5408\u308f\u305b\u554f\u984c<\/h3>\n\n<p class=\"wp-block-paragraph\">\u7279\u306b\u306f\u307e\u308a\u3084\u3059\u3044\u306e\u304c\u300cposition: fixed \u306e\u8981\u7d20\u304c\u3001transform\u304c\u6307\u5b9a\u3055\u308c\u305f\u7956\u5148\u8981\u7d20\u306e\u4e2d\u306b\u3044\u308b\u300d\u30b1\u30fc\u30b9\u3067\u3059\u3002\u672c\u6765fixed\u306f\u30d3\u30e5\u30fc\u30dd\u30fc\u30c8\u57fa\u6e96\u306e\u306f\u305a\u3067\u3059\u304c\u3001<strong>transform\u3092\u6301\u3064\u7956\u5148\u304c\u65b0\u3057\u3044\u300c\u5305\u542b\u30d6\u30ed\u30c3\u30af\u300d\u306b\u306a\u3063\u3066\u3057\u307e\u3046<\/strong>\u305f\u3081\u3001\u30d3\u30e5\u30fc\u30dd\u30fc\u30c8\u56fa\u5b9a\u304c\u5d29\u308c\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-markup\" data-lang=\"HTML\"><code>&lt;!-- \u554f\u984c\u306e\u3042\u308b\u69cb\u9020 --&gt;\n&lt;div class=\"page-wrapper\"&gt; &lt;!-- transform: translateZ(0) \u306a\u3069\u304c\u3042\u308b --&gt;\n  &lt;header class=\"fixed-header\"&gt;&lt;\/header&gt; &lt;!-- position: fixed \u304c\u52b9\u304b\u306a\u304f\u306a\u308b --&gt;\n  &lt;main&gt;...&lt;\/main&gt;\n&lt;\/div&gt;\n<\/code><\/pre><\/div>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>\/* \u554f\u984c\u306e\u3042\u308b.page-wrapper *\/\n.page-wrapper {\n  transform: translateZ(0); \/* GPU\u9ad8\u901f\u5316\u306e\u3064\u3082\u308a\u304cfixed\u8981\u7d20\u3092\u58ca\u3059 *\/\n}\n\n\/* \u76f4\u3057\u65b9: fixed\u8981\u7d20\u306ftransform\u306e\u306a\u3044\u7956\u5148\u306e\u76f4\u4e0b\u306b\u7f6e\u304f *\/\n\/* \u307e\u305f\u306f.page-wrapper\u304b\u3089transform\u3092\u53d6\u308a\u9664\u304d\u3001\n   GPU\u30d2\u30f3\u30c8\u304c\u5fc5\u8981\u306a\u8981\u7d20\u3060\u3051\u306b\u500b\u5225\u306b\u6307\u5b9a\u3059\u308b *\/\n<\/code><\/pre><\/div>\n\n\n<h3 class=\"wp-block-heading\">isolation: isolate\u3067\u610f\u56f3\u7684\u306b\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3092\u4f5c\u308b<\/h3>\n\n<p class=\"wp-block-paragraph\">\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3092\u300cz-index\u3092\u4f7f\u308f\u305a\u306b\u300d\u610f\u56f3\u7684\u306b\u4f5c\u308a\u305f\u3044\u5834\u9762\u304c\u3042\u308a\u307e\u3059\u3002\u305d\u3053\u3067\u4f7f\u3048\u308b\u306e\u304c <strong>isolation: isolate<\/strong> \u3067\u3059\u3002\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3092\u5916\u90e8\u306ez-index\u304b\u3089\u72ec\u7acb\u3055\u305b\u305f\u3044\u5834\u5408\u306b\u6709\u52b9\u3067\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>.component {\n  isolation: isolate; \/* \u65b0\u3057\u3044\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3092\u660e\u793a\u7684\u306b\u5f62\u6210 *\/\n  \/* position\u4e0d\u8981\u3001z-index\u3082\u4e0d\u8981 *\/\n}\n\n\/* \u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u5185\u306e\u8981\u7d20\u306f\u5916\u90e8\u306ez-index\u3068\u7af6\u5408\u3057\u306a\u304f\u306a\u308b *\/\n.component .inner-element {\n  position: relative;\n  z-index: 100; \/* \u3053\u306e\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u5185\u3067\u306e\u307f\u6709\u52b9 *\/\n}\n<\/code><\/pre><\/div>\n\n\n<h2 class=\"wp-block-heading\">\u5b9f\u8df5: \u56fa\u5b9a\u30d8\u30c3\u30c0\u30fc\u30fb\u30c9\u30ed\u30c3\u30d7\u30c0\u30a6\u30f3\u30fb\u30e2\u30fc\u30c0\u30eb\u306e\u91cd\u306a\u308a\u9806\u8a2d\u8a08<\/h2>\n\n\n<h3 class=\"wp-block-heading\">\u56fa\u5b9a\u30d8\u30c3\u30c0\u30fc\uff08position: fixed\uff09<\/h3>\n\n<p class=\"wp-block-paragraph\">\u56fa\u5b9a\u30d8\u30c3\u30c0\u30fc\u306f\u6700\u3082\u57fa\u672c\u7684\u306az-index\u306e\u4f7f\u7528\u4f8b\u3067\u3059\u3002\u30b9\u30af\u30ed\u30fc\u30eb\u3057\u3066\u3082\u30b3\u30f3\u30c6\u30f3\u30c4\u306e\u4e0a\u306b\u8868\u793a\u3055\u308c\u7d9a\u3051\u308b\u3088\u3046\u3001\u5341\u5206\u306b\u9ad8\u3044z-index\u3092\u4e0e\u3048\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>.site-header {\n  position: fixed;\n  top: 0;\n  left: 0;\n  width: 100%;\n  height: 60px;\n  background: #fff;\n  z-index: 100; \/* \u30b3\u30f3\u30c6\u30f3\u30c4\u3088\u308a\u524d\u9762 *\/\n  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);\n}\n\n\/* \u30d8\u30c3\u30c0\u30fc\u5206\u306e\u4f59\u767d\u3092main\u306b\u8a2d\u5b9a *\/\n.site-main {\n  padding-top: 60px;\n}\n<\/code><\/pre><\/div>\n\n\n<h3 class=\"wp-block-heading\">\u30c9\u30ed\u30c3\u30d7\u30c0\u30a6\u30f3\u30e1\u30cb\u30e5\u30fc<\/h3>\n\n<p class=\"wp-block-paragraph\">\u30ca\u30d3\u30b2\u30fc\u30b7\u30e7\u30f3\u306e\u30c9\u30ed\u30c3\u30d7\u30c0\u30a6\u30f3\u30e1\u30cb\u30e5\u30fc\u306f\u3001\u30d8\u30c3\u30c0\u30fc\u306e\u5b50\u8981\u7d20\u3068\u3057\u3066\u914d\u7f6e\u3055\u308c\u308b\u305f\u3081\u3001\u30d8\u30c3\u30c0\u30fc\u306e\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u5185\u306b\u542b\u307e\u308c\u307e\u3059\u3002\u30d8\u30c3\u30c0\u30fc\u81ea\u4f53\u304c\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3092\u5f62\u6210\u3057\u3066\u3044\u308b\u5834\u5408\u3001\u30c9\u30ed\u30c3\u30d7\u30c0\u30a6\u30f3\u306f\u30d8\u30c3\u30c0\u30fc\u5185\u306ez-index\u3067\u5236\u5fa1\u3057\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-markup\" data-lang=\"HTML\"><code>&lt;header class=\"site-header\"&gt;\n  &lt;nav class=\"global-nav\"&gt;\n    &lt;ul&gt;\n      &lt;li class=\"nav-item has-dropdown\"&gt;\n        &lt;a href=\"#\"&gt;\u30e1\u30cb\u30e5\u30fc&lt;\/a&gt;\n        &lt;ul class=\"dropdown-menu\"&gt;\n          &lt;li&gt;&lt;a href=\"#\"&gt;\u30b5\u30d6\u30e1\u30cb\u30e5\u30fc1&lt;\/a&gt;&lt;\/li&gt;\n          &lt;li&gt;&lt;a href=\"#\"&gt;\u30b5\u30d6\u30e1\u30cb\u30e5\u30fc2&lt;\/a&gt;&lt;\/li&gt;\n        &lt;\/ul&gt;\n      &lt;\/li&gt;\n    &lt;\/ul&gt;\n  &lt;\/nav&gt;\n&lt;\/header&gt;\n<\/code><\/pre><\/div>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>.site-header {\n  position: fixed;\n  z-index: 100;\n  \/* \u3053\u3053\u3067z-index\u3092\u6307\u5b9a\u3059\u308b\u3068\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u304c\u751f\u6210\u3055\u308c\u308b *\/\n  \/* \u30c9\u30ed\u30c3\u30d7\u30c0\u30a6\u30f3\u306f\u3053\u306e\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u5185\u306b\u542b\u307e\u308c\u308b *\/\n}\n\n.nav-item {\n  position: relative; \/* \u30c9\u30ed\u30c3\u30d7\u30c0\u30a6\u30f3\u306e\u57fa\u6e96\u70b9 *\/\n}\n\n.dropdown-menu {\n  position: absolute;\n  top: 100%;\n  left: 0;\n  z-index: 10; \/* \u30d8\u30c3\u30c0\u30fc\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u5185\u3067\u306e\u524d\u9762\u914d\u7f6e *\/\n  display: none;\n  background: #fff;\n  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);\n  min-width: 200px;\n}\n\n.nav-item:hover .dropdown-menu {\n  display: block;\n}\n<\/code><\/pre><\/div>\n\n\n<h3 class=\"wp-block-heading\">\u30e2\u30fc\u30c0\u30eb\u30c0\u30a4\u30a2\u30ed\u30b0<\/h3>\n\n<p class=\"wp-block-paragraph\">\u30e2\u30fc\u30c0\u30eb\u306f\u30da\u30fc\u30b8\u306e\u6700\u524d\u9762\u306b\u8868\u793a\u3059\u308b\u5fc5\u8981\u304c\u3042\u308a\u307e\u3059\u3002\u6700\u3082\u78ba\u5b9f\u306a\u5b9f\u88c5\u65b9\u6cd5\u306f\u3001<strong>\u30e2\u30fc\u30c0\u30eb\u3092body\u306e\u76f4\u63a5\u306e\u5b50\u8981\u7d20\u3068\u3057\u3066\u914d\u7f6e\u3059\u308b<\/strong>\u3053\u3068\u3067\u3059\u3002\u3053\u308c\u306b\u3088\u308a\u3001\u3069\u306e\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u306b\u3082\u9589\u3058\u8fbc\u3081\u3089\u308c\u307e\u305b\u3093\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-markup\" data-lang=\"HTML\"><code>&lt;!-- body\u306e\u76f4\u4e0b\u306b\u914d\u7f6e\u3059\u308b\u306e\u304c\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9 --&gt;\n&lt;body&gt;\n  &lt;div id=\"app\"&gt;\n    &lt;!-- \u30e1\u30a4\u30f3\u30b3\u30f3\u30c6\u30f3\u30c4 --&gt;\n  &lt;\/div&gt;\n\n  &lt;!-- \u30e2\u30fc\u30c0\u30eb\u306fapp\u5916\u3001body\u76f4\u4e0b --&gt;\n  &lt;div class=\"modal-overlay\" id=\"modal\"&gt;\n    &lt;div class=\"modal-dialog\"&gt;\n      &lt;button class=\"modal-close\"&gt;&amp;times;&lt;\/button&gt;\n      &lt;div class=\"modal-content\"&gt;\n        &lt;p&gt;\u30e2\u30fc\u30c0\u30eb\u306e\u5185\u5bb9&lt;\/p&gt;\n      &lt;\/div&gt;\n    &lt;\/div&gt;\n  &lt;\/div&gt;\n&lt;\/body&gt;\n<\/code><\/pre><\/div>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>.modal-overlay {\n  position: fixed;\n  inset: 0; \/* top\/right\/bottom\/left: 0 \u306e\u77ed\u7e2e\u5f62 *\/\n  background: rgba(0, 0, 0, 0.6);\n  z-index: 1000; \/* \u30d8\u30c3\u30c0\u30fc(100)\u3088\u308a\u5927\u304d\u3044\u5024 *\/\n  display: flex;\n  align-items: center;\n  justify-content: center;\n  \/* \u975e\u8868\u793a\u6642 *\/\n  opacity: 0;\n  pointer-events: none;\n  transition: opacity 0.3s;\n}\n\n.modal-overlay.is-open {\n  opacity: 1;\n  pointer-events: auto;\n}\n\n.modal-dialog {\n  position: relative;\n  background: #fff;\n  border-radius: 8px;\n  padding: 32px;\n  max-width: 560px;\n  width: 90%;\n  max-height: 80vh;\n  overflow-y: auto;\n}\n\n.modal-close {\n  position: absolute;\n  top: 12px;\n  right: 16px;\n  background: none;\n  border: none;\n  font-size: 24px;\n  cursor: pointer;\n  color: #51322b;\n}\n<\/code><\/pre><\/div>\n\n<p class=\"wp-block-paragraph\">\u307e\u305f\u3001HTML\u6a19\u6e96\u306e <strong>&lt;dialog&gt; \u8981\u7d20<\/strong>\uff082026\u5e74\u6642\u70b9\u3067\u307b\u307c\u5168\u30e2\u30c0\u30f3\u30d6\u30e9\u30a6\u30b6\u5bfe\u5fdc\uff09\u3092\u4f7f\u3046\u3068\u3001\u30d6\u30e9\u30a6\u30b6\u304c\u6700\u4e0a\u4f4d\u30ec\u30a4\u30e4\u30fc\u306b\u81ea\u52d5\u7684\u306b\u914d\u7f6e\u3059\u308b\u305f\u3081\u3001z-index\u306e\u7ba1\u7406\u304b\u3089\u89e3\u653e\u3055\u308c\u308b\u30b1\u30fc\u30b9\u304c\u5897\u3048\u3066\u3044\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-markup\" data-lang=\"HTML\"><code>&lt;!-- dialog\u8981\u7d20\u3092\u4f7f\u3046\u73fe\u4ee3\u7684\u306a\u66f8\u304d\u65b9 --&gt;\n&lt;dialog id=\"my-modal\"&gt;\n  &lt;p&gt;\u30e2\u30fc\u30c0\u30eb\u306e\u5185\u5bb9&lt;\/p&gt;\n  &lt;button id=\"close-btn\"&gt;\u9589\u3058\u308b&lt;\/button&gt;\n&lt;\/dialog&gt;\n\n&lt;button id=\"open-btn\"&gt;\u30e2\u30fc\u30c0\u30eb\u3092\u958b\u304f&lt;\/button&gt;\n<\/code><\/pre><\/div>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>\/* dialog\u8981\u7d20\u306f\u30d6\u30e9\u30a6\u30b6\u304c\u6700\u4e0a\u4f4d\u30ec\u30a4\u30e4\u30fc\u306b\u914d\u7f6e\u3059\u308b\u305f\u3081\n   z-index\u3092\u6c17\u306b\u3059\u308b\u5fc5\u8981\u304c\u307b\u307c\u306a\u3044 *\/\ndialog {\n  border: none;\n  border-radius: 8px;\n  padding: 32px;\n  max-width: 560px;\n  width: 90%;\n}\n\ndialog::backdrop {\n  background: rgba(0, 0, 0, 0.6);\n}\n<\/code><\/pre><\/div>\n\n\n<h3 class=\"wp-block-heading\">\u30c8\u30fc\u30b9\u30c8\u901a\u77e5\u30fb\u30c4\u30fc\u30eb\u30c1\u30c3\u30d7<\/h3>\n\n<p class=\"wp-block-paragraph\">\u753b\u9762\u53f3\u4e0b\u306b\u8868\u793a\u3059\u308b\u30c8\u30fc\u30b9\u30c8\u901a\u77e5\u3084\u3001\u8981\u7d20\u306e\u30db\u30d0\u30fc\u6642\u306b\u8868\u793a\u3059\u308b\u30c4\u30fc\u30eb\u30c1\u30c3\u30d7\u3082\u56fa\u5b9a\u30fb\u7d76\u5bfe\u914d\u7f6e\u3068z-index\u306e\u7d44\u307f\u5408\u308f\u305b\u3067\u5b9f\u88c5\u3057\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>\/* \u30c8\u30fc\u30b9\u30c8\u901a\u77e5 *\/\n.toast-container {\n  position: fixed;\n  bottom: 24px;\n  right: 24px;\n  z-index: 900; \/* \u30d8\u30c3\u30c0\u30fc(100)\u3068\u30e2\u30fc\u30c0\u30eb(1000)\u306e\u9593 *\/\n  display: flex;\n  flex-direction: column;\n  gap: 8px;\n}\n\n.toast {\n  background: #51322b;\n  color: #fff;\n  padding: 12px 20px;\n  border-radius: 6px;\n  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);\n  animation: slide-in 0.3s ease;\n}\n\n@keyframes slide-in {\n  from { transform: translateX(120%); }\n  to   { transform: translateX(0); }\n}\n\n\/* \u30c4\u30fc\u30eb\u30c1\u30c3\u30d7 *\/\n.tooltip-wrapper {\n  position: relative;\n  display: inline-block;\n}\n\n.tooltip {\n  position: absolute;\n  bottom: calc(100% + 8px);\n  left: 50%;\n  transform: translateX(-50%);\n  background: #333;\n  color: #fff;\n  padding: 6px 12px;\n  border-radius: 4px;\n  white-space: nowrap;\n  font-size: 0.8rem;\n  z-index: 50;\n  pointer-events: none;\n  opacity: 0;\n  transition: opacity 0.2s;\n}\n\n.tooltip-wrapper:hover .tooltip {\n  opacity: 1;\n}\n<\/code><\/pre><\/div>\n\n\n<h2 class=\"wp-block-heading\">z-index\u5024\u306e\u8a2d\u8a08\u30fb\u7ba1\u7406\u8853<\/h2>\n\n\n<h3 class=\"wp-block-heading\">\u30de\u30b8\u30c3\u30af\u30ca\u30f3\u30d0\u30fc\u306f\u907f\u3051\u308b\u2014\u2014CSS\u5909\u6570\uff08\u30ab\u30b9\u30bf\u30e0\u30d7\u30ed\u30d1\u30c6\u30a3\uff09\u3067\u7ba1\u7406<\/h3>\n\n<p class=\"wp-block-paragraph\">\u30d7\u30ed\u30b8\u30a7\u30af\u30c8\u304c\u5927\u304d\u304f\u306a\u308b\u3068\u3001\u3042\u3061\u3053\u3061\u306b\u6563\u3089\u3070\u3063\u305f z-index: 9999 \u3084 z-index: 999999 \u304c\u885d\u7a81\u3057\u305f\u308a\u3001\u3069\u308c\u304c\u6b63\u3057\u3044\u5024\u304b\u308f\u304b\u3089\u306a\u304f\u306a\u3063\u305f\u308a\u3057\u307e\u3059\u3002CSS\u5909\u6570\uff08\u30ab\u30b9\u30bf\u30e0\u30d7\u30ed\u30d1\u30c6\u30a3\uff09\u3092\u4f7f\u3063\u3066z-index\u3092\u4e00\u5143\u7ba1\u7406\u3059\u308b\u306e\u304c\u30e2\u30c0\u30f3\u306a\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9\u3067\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>\/* :root \u3067z-index\u3092\u307e\u3068\u3081\u3066\u5b9a\u7fa9 *\/\n:root {\n  --z-below:    -1;\n  --z-base:      0;\n  --z-raised:   10;  \/* \u30ab\u30fc\u30c9\u30fb\u5c0f\u8981\u7d20\u306e\u91cd\u306a\u308a *\/\n  --z-dropdown: 100; \/* \u30c9\u30ed\u30c3\u30d7\u30c0\u30a6\u30f3 *\/\n  --z-sticky:   200; \/* \u56fa\u5b9a\u30d8\u30c3\u30c0\u30fc\u30fb\u30b9\u30c6\u30a3\u30c3\u30ad\u30fc\u8981\u7d20 *\/\n  --z-overlay:  300; \/* \u30aa\u30fc\u30d0\u30fc\u30ec\u30a4\u30fb\u80cc\u666f\u5e55 *\/\n  --z-modal:    400; \/* \u30e2\u30fc\u30c0\u30eb\u30c0\u30a4\u30a2\u30ed\u30b0 *\/\n  --z-toast:    500; \/* \u30c8\u30fc\u30b9\u30c8\u30fb\u901a\u77e5 *\/\n  --z-tooltip:  600; \/* \u30c4\u30fc\u30eb\u30c1\u30c3\u30d7 *\/\n}\n\n\/* \u5404\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3067\u5909\u6570\u3092\u53c2\u7167 *\/\n.site-header {\n  position: fixed;\n  z-index: var(--z-sticky);\n}\n\n.modal-overlay {\n  position: fixed;\n  z-index: var(--z-modal);\n}\n\n.toast-container {\n  position: fixed;\n  z-index: var(--z-toast);\n}\n<\/code><\/pre><\/div>\n\n<p class=\"wp-block-paragraph\">\u5024\u3092\u5909\u66f4\u3057\u305f\u3044\u3068\u304d\u306f :root \u306e\u5b9a\u7fa9\u30921\u884c\u76f4\u3059\u3060\u3051\u3067\u5168\u4f53\u306b\u53cd\u6620\u3055\u308c\u307e\u3059\u3002\u307e\u305f\u3001\u30d5\u30a1\u30a4\u30eb\u306e\u5148\u982d\u3092\u898b\u308c\u3070\u30d7\u30ed\u30b8\u30a7\u30af\u30c8\u306ez-index\u8a2d\u8a08\u304c\u4e00\u76ee\u77ad\u7136\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n\n\n<h3 class=\"wp-block-heading\">SCSS\u3092\u4f7f\u3046\u5834\u5408\u306f\u30de\u30c3\u30d7\u3067\u7ba1\u7406<\/h3>\n\n<p class=\"wp-block-paragraph\">Sass\/SCSS\u3092\u63a1\u7528\u3057\u3066\u3044\u308b\u30d7\u30ed\u30b8\u30a7\u30af\u30c8\u3067\u306f\u3001\u30de\u30c3\u30d7\uff08Map\uff09\u3092\u4f7f\u3063\u305f\u7ba1\u7406\u3082\u3088\u304f\u4f7f\u308f\u308c\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>\/* _z-index.scss *\/\n$z-layers: (\n  \"below\":    -1,\n  \"base\":      0,\n  \"raised\":   10,\n  \"dropdown\": 100,\n  \"sticky\":   200,\n  \"overlay\":  300,\n  \"modal\":    400,\n  \"toast\":    500,\n  \"tooltip\":  600\n);\n\n\/* \u53d6\u308a\u51fa\u3059function\u3092\u5b9a\u7fa9 *\/\n@function z($layer) {\n  @return map-get($z-layers, $layer);\n}\n\n\/* \u4f7f\u7528\u4f8b *\/\n.site-header {\n  z-index: z(\"sticky\"); \/* 200 *\/\n}\n\n.modal-overlay {\n  z-index: z(\"modal\"); \/* 400 *\/\n}\n<\/code><\/pre><\/div>\n\n\n<h3 class=\"wp-block-heading\">z-index\u306e\u5024\u306b\u306f10\u523b\u307f\u30fb100\u523b\u307f\u3092\u4f7f\u3046<\/h3>\n\n<p class=\"wp-block-paragraph\">z-index\u306e\u5024\u306f\u300c1, 2, 3&#8230;\u300d\u3068\u9023\u756a\u306b\u3059\u308b\u3088\u308a\u3001<strong>10\u3084100\u523b\u307f<\/strong>\u306b\u3057\u3066\u304a\u304f\u3068\u3001\u5f8c\u304b\u3089\u300c\u3053\u306e\u8981\u7d20\u3092\u65e2\u5b58\u306e2\u3064\u306e\u9593\u306b\u631f\u307f\u305f\u3044\u300d\u3068\u3044\u3046\u30b1\u30fc\u30b9\u3067\u67d4\u8edf\u306b\u5bfe\u5fdc\u3067\u304d\u307e\u3059\u3002z-index: 99999 \u306e\u3088\u3046\u306a\u6975\u7aef\u306a\u5024\u306f\u3001\u305d\u308c\u304c\u5fc5\u8981\u306b\u306a\u3063\u305f\u6642\u70b9\u3067\u8a2d\u8a08\u306e\u898b\u76f4\u3057\u30b5\u30a4\u30f3\u3068\u6349\u3048\u307e\u3057\u3087\u3046\u3002<\/p>\n\n\n<h2 class=\"wp-block-heading\">\u3088\u304f\u3042\u308b\u30df\u30b9\u3068\u30c7\u30d0\u30c3\u30b0\u306e\u30b3\u30c4<\/h2>\n\n\n<h3 class=\"wp-block-heading\">\u30d6\u30e9\u30a6\u30b6\u958b\u767a\u8005\u30c4\u30fc\u30eb\u3067\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3092\u78ba\u8a8d\u3059\u308b<\/h3>\n\n<p class=\"wp-block-paragraph\">Chrome DevTools \u3067\u306f\u3001\u300cElements\u300d\u30d1\u30cd\u30eb\u3067\u8981\u7d20\u3092\u9078\u629e\u3057\u300cComputed\u300d\u30bf\u30d6\u306e\u300cz-index\u300d\u3092\u78ba\u8a8d\u3067\u304d\u307e\u3059\u3002\u307e\u305f\u3001Firefox DevTools \u3067\u306f\u300c3D\u30d3\u30e5\u30fc\u300d\u6a5f\u80fd\u3067\u30da\u30fc\u30b8\u306e\u91cd\u306a\u308a\u69cb\u9020\u3092\u7acb\u4f53\u7684\u306b\u53ef\u8996\u5316\u3067\u304d\u307e\u3059\uff08DevTools \u2192 \u305d\u306e\u4ed6\u30c4\u30fc\u30eb \u2192 \u30ec\u30a4\u30e4\u30fc\uff09\u3002<\/p>\n\n\n<h3 class=\"wp-block-heading\">\u3088\u304f\u3042\u308b\u30df\u30b9\u306e\u30c1\u30a7\u30c3\u30af\u30ea\u30b9\u30c8<\/h3>\n\n<ul class=\"wp-block-list\">\n<li>position\u3092\u4ed8\u3051\u5fd8\u308c\u3066\u3044\u306a\u3044\u304b<\/li>\n<li>\u6bd4\u8f03\u3057\u305f\u3044\u8981\u7d20\u304c\u540c\u3058\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u5185\u306b\u3044\u308b\u304b<\/li>\n<li>\u89aa\u8981\u7d20\u306btransform \/ opacity \/ filter\u304c\u304b\u304b\u3063\u3066\u3044\u306a\u3044\u304b<\/li>\n<li>position: fixed \u306e\u8981\u7d20\u306e\u7956\u5148\u306btransform\u304c\u306a\u3044\u304b<\/li>\n<li>z-index\u306e\u5024\u304c\u610f\u56f3\u3057\u305f\u901a\u308a\u306b\u8a2d\u8a08\u3055\u308c\u3066\u3044\u308b\u304b\uff08\u30de\u30b8\u30c3\u30af\u30ca\u30f3\u30d0\u30fc\u306b\u306a\u3063\u3066\u3044\u306a\u3044\u304b\uff09<\/li>\n<li>will-change\u3092\u4e0d\u5fc5\u8981\u306b\u4f7f\u3063\u3066\u3044\u306a\u3044\u304b<\/li>\n<\/ul>\n\n\n<h2 class=\"wp-block-heading\">\u3088\u304f\u3042\u308b\u8cea\u554f\uff08FAQ\uff09<\/h2>\n\n\n<h3 class=\"wp-block-heading\">Q. z-index: 9999 \u306b\u3057\u3066\u3082\u524d\u306b\u6765\u306a\u3044\u3002\u3069\u3046\u3059\u308c\u3070\u826f\u3044\u3067\u3059\u304b\uff1f<\/h3>\n\n<p class=\"wp-block-paragraph\">\u307b\u307c\u78ba\u5b9f\u306b\u3001\u5bfe\u8c61\u8981\u7d20\u307e\u305f\u306f\u305d\u306e\u7956\u5148\u8981\u7d20\u304c\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u306b\u9589\u3058\u8fbc\u3081\u3089\u308c\u3066\u3044\u307e\u3059\u3002\u307e\u305a\u3001\u305d\u306e\u8981\u7d20\u306e\u89aa\u8981\u7d20\u3092\u3059\u3079\u3066\u9061\u3063\u3066\u3001position + z-index \/ opacity \/ transform \/ filter \u304c\u6307\u5b9a\u3055\u308c\u3066\u3044\u308b\u8981\u7d20\u304c\u306a\u3044\u304b\u78ba\u8a8d\u3057\u3066\u304f\u3060\u3055\u3044\u3002\u898b\u3064\u304b\u3063\u305f\u3089\u3001\u305d\u306e\u89aa\u304b\u3089z-index\u3092\u524a\u9664\u3059\u308b\u304b\u3001\u5bfe\u8c61\u8981\u7d20\u3092\u305d\u306e\u89aa\u306e\u5916\u306eDOM\u306b\u79fb\u52d5\u3055\u305b\u308b\u3053\u3068\u3067\u89e3\u6c7a\u3057\u307e\u3059\u3002<\/p>\n\n\n<h3 class=\"wp-block-heading\">Q. z-index: -1 \u3092\u4f7f\u3046\u3068\u3069\u3046\u306a\u308a\u307e\u3059\u304b\uff1f<\/h3>\n\n<p class=\"wp-block-paragraph\">z-index: -1 \u3092\u6307\u5b9a\u3059\u308b\u3068\u3001\u305d\u306e\u8981\u7d20\u306f\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u5185\u306e\u300c\u901a\u5e38\u30d5\u30ed\u30fc\u306e\u8981\u7d20\u300d\u3088\u308a\u3082\u5f8c\u308d\uff08\u5965\uff09\u306b\u914d\u7f6e\u3055\u308c\u307e\u3059\u3002\u80cc\u666f\u306e\u88c5\u98fe\u7684\u306a\u8981\u7d20\u3092\u30b3\u30f3\u30c6\u30f3\u30c4\u306e\u5f8c\u308d\u306b\u914d\u7f6e\u3057\u305f\u3044\u3068\u304d\u306b\u4f7f\u3044\u307e\u3059\u3002\u305f\u3060\u3057\u3001\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3092\u6301\u3064\u7956\u5148\u306e\u80cc\u666f\u3088\u308a\u306f\u524d\u9762\u306b\u7559\u307e\u308b\u305f\u3081\u3001\u3055\u3089\u306b\u5965\u306b\u96a0\u3057\u305f\u3044\u5834\u5408\u306f\u3001DOM\u306e\u69cb\u9020\u3092\u5909\u3048\u308b\u304b isolation: isolate \u3092\u4f7f\u3063\u3066\u8abf\u6574\u3057\u307e\u3059\u3002<\/p>\n\n\n<h3 class=\"wp-block-heading\">Q. opacity: 0 \u306b\u3057\u305f\u8981\u7d20\u3082\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3092\u4f5c\u308a\u307e\u3059\u304b\uff1f<\/h3>\n\n<p class=\"wp-block-paragraph\">\u306f\u3044\u3001\u4f5c\u308a\u307e\u3059\u3002opacity: 0 \u306f\u8996\u899a\u7684\u306b\u306f\u898b\u3048\u307e\u305b\u3093\u304c\u3001CSS\u306e\u4ed5\u69d8\u4e0a\u306f\u300copacity \u304c 1 \u672a\u6e80\u306e\u8981\u7d20\u300d\u306b\u8a72\u5f53\u3059\u308b\u305f\u3081\u3001\u30b9\u30bf\u30c3\u30ad\u30f3\u30b0\u30b3\u30f3\u30c6\u30ad\u30b9\u30c8\u3092\u751f\u6210\u3057\u307e\u3059\u3002\u307e\u305f\u3001opacity: 0 \u306b\u3057\u305f\u3060\u3051\u3067\u306f\u30dd\u30a4\u30f3\u30bf\u30fc\u30a4\u30d9\u30f3\u30c8\u3082\u53d7\u3051\u4ed8\u3051\u7d9a\u3051\u307e\u3059\u3002\u5b8c\u5168\u306b\u975e\u8868\u793a\u306b\u3057\u305f\u3044\u5834\u5408\u306f visibility: hidden \u3084 display: none \u3068\u306e\u7d44\u307f\u5408\u308f\u305b\u3092\u691c\u8a0e\u3057\u3066\u304f\u3060\u3055\u3044\u3002<\/p>\n\n\n<h3 class=\"wp-block-heading\">Q. React\u306a\u3069\u306e\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u8a2d\u8a08\u3067z-index\u3092\u7ba1\u7406\u3059\u308b\u826f\u3044\u65b9\u6cd5\u306f\uff1f<\/h3>\n\n<p class=\"wp-block-paragraph\">React\u306a\u3069\u3067\u306f\u3001\u30e2\u30fc\u30c0\u30eb\u30fb\u30c9\u30ed\u30c3\u30d7\u30c0\u30a6\u30f3\u30fb\u30c8\u30fc\u30b9\u30c8\u306a\u3069\u306eUI\u8981\u7d20\u3092<strong>React 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