:root {
    --bg-color: #F5F5F7;
    --text-main: #1d1d1f;
    --text-muted: #86868B;
    --glass-bg: rgba(255, 255, 255, 0.72);
    --glass-border: rgba(0, 0, 0, 0.08);
    --glass-hover: rgba(0, 0, 0, 0.04);
    --shadow-glow: rgba(0, 0, 0, 0.06);
    --card-bg: #ffffff;
}

.dark {
    --bg-color: #000000;
    --text-main: #f5f5f7;
    --text-muted: #8E8E93;
    --glass-bg: rgba(0, 0, 0, 0.72);
    --glass-border: rgba(255, 255, 255, 0.10);
    --glass-hover: rgba(255, 255, 255, 0.08);
    --shadow-glow: rgba(0, 0, 0, 0.5);
    --card-bg: #1C1C1E;
}

body {
    background-color: var(--bg-color);
    color: var(--text-main);
    transition: background-color 0.3s ease, color 0.3s ease;
    -webkit-tap-highlight-color: transparent;
    overflow-x: hidden;
    overflow-y: auto;
}

a { color: inherit; text-decoration: none; }

::selection { background: var(--text-main); color: var(--bg-color); }

/* No background grid in the Apple-clean theme (class kept for compatibility) */
.bg-grid { background-image: none; }

/* Frosted header */
.glass-header {
    background: var(--glass-bg);
    backdrop-filter: blur(24px);
    -webkit-backdrop-filter: blur(24px);
    border-bottom: 1px solid var(--glass-border);
}

/* Solid Apple cards / panels */
.glass-panel {
    background: var(--card-bg);
    border: 1px solid var(--glass-border);
    box-shadow: 0 4px 24px var(--shadow-glow);
}

::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--glass-border); border-radius: 6px; }
::-webkit-scrollbar-thumb:hover { background: var(--text-muted); }

.category-btn {
    transition: all 0.25s ease;
}
.category-btn.active,
.category-btn.active:hover,
.category-btn.active:focus {
    background: var(--text-main) !important;
    color: var(--bg-color) !important;
    border-color: var(--text-main) !important;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}
.animate-fade-in {
    animation: fadeIn 0.6s cubic-bezier(0.2, 0.8, 0.2, 1) forwards;
    opacity: 0;
}

.no-scrollbar::-webkit-scrollbar { display: none; }
.no-scrollbar { -ms-overflow-style: none; scrollbar-width: none; }

.search-input:focus { outline: none; background: var(--card-bg); }

/* Category badges — monochrome (Apple-clean) */
.badge-cat-research,
.badge-cat-tech,
.badge-cat-cases,
.badge-cat-thoughts,
.badge-cat-news,
.badge-cat-announcements {
    color: var(--text-main);
    border-color: var(--glass-border);
    background: var(--glass-hover);
}

/* Title hover — subtle fade, no color (Apple-clean) */
.title-hover-research,
.title-hover-tech,
.title-hover-cases,
.title-hover-thoughts,
.title-hover-news,
.title-hover-announcements { transition: opacity 0.2s ease; }
.group:hover .title-hover-research,
.group:hover .title-hover-tech,
.group:hover .title-hover-cases,
.group:hover .title-hover-thoughts,
.group:hover .title-hover-news,
.group:hover .title-hover-announcements { opacity: 0.55; }

/* Calendar */
.cal-day {
    aspect-ratio: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 999px;
    font-family: "Space Mono", monospace;
    font-size: 12px;
    color: var(--text-muted);
    cursor: default;
    user-select: none;
    border: 1px solid transparent;
}
.cal-day.has-posts { color: var(--text-main); border-color: var(--glass-border); cursor: pointer; }
.cal-day.has-posts:hover { background: var(--glass-hover); }
.cal-day.active { background: var(--text-main); color: var(--bg-color); border-color: var(--text-main); }
.cal-day.empty { visibility: hidden; }

/* Article body */
.prose-feed h1 { font-size: 1.75rem; font-weight: 700; margin: 1.4em 0 .6em; font-family: -apple-system, BlinkMacSystemFont, "Inter", sans-serif; letter-spacing: -0.02em; }
.prose-feed h2 { font-size: 1.4rem;  font-weight: 700; margin: 1.4em 0 .6em; font-family: -apple-system, BlinkMacSystemFont, "Inter", sans-serif; letter-spacing: -0.02em; }
.prose-feed h3 { font-size: 1.15rem; font-weight: 700; margin: 1.2em 0 .5em; font-family: -apple-system, BlinkMacSystemFont, "Inter", sans-serif; }
.prose-feed p  { margin: .9em 0; line-height: 1.7; color: var(--text-main); }
.prose-feed ul,
.prose-feed ol { padding-left: 1.4em; margin: .8em 0; color: var(--text-main); }
.prose-feed li { margin: .35em 0; line-height: 1.65; }
.prose-feed a  { color: var(--text-main); text-decoration: underline; text-underline-offset: 3px; text-decoration-thickness: 1px; }
.prose-feed code {
    font-family: "Space Mono", monospace;
    font-size: .9em;
    background: var(--glass-hover);
    padding: .15em .4em;
    border-radius: .35em;
}
.prose-feed pre {
    background: var(--glass-hover);
    border: 1px solid var(--glass-border);
    border-radius: 1rem;
    padding: 1rem 1.25rem;
    overflow-x: auto;
    margin: 1.2em 0;
}
.prose-feed pre code { background: transparent; padding: 0; }
.prose-feed blockquote {
    border-left: 3px solid var(--text-main);
    margin: 1em 0;
    padding: .2em 1em;
    color: var(--text-muted);
    font-style: italic;
}

/* scroll-top button visibility helper */
#scroll-top-btn.visible { opacity: 1; pointer-events: auto; }