body {
    margin: 0;
    font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
    background: #111;
    color: #eee;
}

header {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 56px;
    display: flex;
    align-items: center;
    padding: 0 12px;
    box-sizing: border-box;
    background: rgba(0, 0, 0, 0.85);
    backdrop-filter: blur(6px);
    z-index: 1000;
}

.brand {
    margin-left: 8px;
    font-size: 16px;
    letter-spacing: 0.08em;
}

.hamburger {
    width: 32px;
    height: 32px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    gap: 4px;
    cursor: pointer;
}

.hamburger span {
    height: 2px;
    width: 20px;
    background: #eee;
    display: block;
    transition: transform 0.2s ease, opacity 0.2s ease;
}

/* 開閉アニメーション */
.menu-open .hamburger span:nth-child(1) {
    transform: translateY(6px) rotate(45deg);
}
.menu-open .hamburger span:nth-child(2) {
    opacity: 0;
}
.menu-open .hamburger span:nth-child(3) {
    transform: translateY(-6px) rotate(-45deg);
}
nav {
    position: fixed;
    top: 56px;
    left: 0;
    width: 260px;
    height: calc(100% - 56px);
    background: #181818;
    border-right: 1px solid #333;
    transform: translateX(-100%);
    transition: transform 0.2s ease-out;
    padding: 16px 0;
    box-sizing: border-box;
    z-index: 900;
}

.menu-open nav {
    transform: translateX(0);
}

nav ul {
    list-style: none;
    margin: 0;
    padding: 0;
}

nav li {
    margin: 0;
}

nav a {
    display: block;
    padding: 10px 20px;
    color: #ddd;
    text-decoration: none;
    font-size: 14px;
}

nav a:hover {
    background: #252525;
    color: #fff;
}

main {
    max-width: 960px;
    margin: 0 auto;
    box-sizing: border-box;
}

h1, h2, h3 {
    font-weight: 600;
}

a {
    color: #7fd1ff;
}

.tag {
    display: inline-block;
    font-size: 10px;
    padding: 2px 6px;
    border-radius: 999px;
    background: #222;
    margin-left: 6px;
    color: #aaa;
}