/* ==========================================================================
   base.css — Design Foundation for alexdavydov.github.io
   ==========================================================================

   AESTHETIC: Apple / Notion — white, clean, readable.

   PURPOSE
   -------
   Shared design tokens + safe defaults for the entire site.
   Loaded BEFORE any page-specific <style> so that inline rules
   naturally override these defaults (same specificity, later wins).

   SAFETY CONTRACT
   ---------------
   - No !important — ever.
   - All visual properties use CSS custom properties (--var).
   - Page-specific <style> blocks keep full control.
   - Adding this file to an existing page must not change its appearance
     unless the page was already relying on browser defaults.

   TOKEN NAMING
   ------------
   --color-*    colours
   --font-*     font stacks
   --lh-*       line-heights
   --space-*    spacing scale
   --radius-*   border radii
   --shadow-*   box shadows
   --t-*        transitions / durations
   --max-*      max-width constraints

   LAST UPDATED: 2026-02-13
   ========================================================================== */


/* ---------- 1. Design Tokens ------------------------------------------- */

:root {
    /* --- Colours: neutrals --- */
    --color-text:           #111111;
    --color-text-muted:     rgba(17, 17, 17, 0.68);
    --color-text-faint:     rgba(17, 17, 17, 0.48);
    --color-bg:             #ffffff;
    --color-bg-subtle:      #f6f7f8;
    --color-bg-muted:       #f1f2f4;
    --color-border:         rgba(17, 17, 17, 0.10);
    --color-border-hover:   rgba(17, 17, 17, 0.16);

    /* --- Colours: semantic --- */
    --color-accent:         #0071e3;
    --color-accent-hover:   #0062c4;
    --color-link:           #0071e3;
    --color-link-hover:     #0062c4;
    --color-positive:       #047857;
    --color-positive-bg:    #d1fae5;
    --color-warning:        #b45309;
    --color-warning-bg:     #fef3c7;
    --color-negative:       #dc2626;

    /* --- Typography --- */
    --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI',
                 'Helvetica Neue', Arial, sans-serif;
    --font-mono: ui-monospace, 'SF Mono', 'Cascadia Code',
                 'Consolas', monospace;
    --lh-base:   1.65;
    --lh-tight:  1.35;
    --lh-loose:  1.75;

    /* --- Spacing scale --- */
    --space-xs:  4px;
    --space-sm:  10px;
    --space-md:  14px;
    --space-lg:  18px;
    --space-xl:  24px;
    --space-2xl: 32px;
    --space-3xl: 48px;

    /* --- Sizing --- */
    --max-container: 980px;
    --max-content:   740px;

    /* --- Border radii --- */
    --radius-sm: 10px;
    --radius-md: 12px;
    --radius-lg: 16px;

    /* --- Box shadows --- */
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.06);
    --shadow-md: 0 10px 30px rgba(0, 0, 0, 0.08);
    --shadow-lg: 0 20px 50px rgba(0, 0, 0, 0.10);

    /* --- Transitions --- */
    --t-fast:    120ms ease;
    --t-default: 180ms ease;
}


/* ---------- 2. Minimal Reset ------------------------------------------- */

*,
*::before,
*::after {
    box-sizing: border-box;
}


/* ---------- 3. Base Typography ----------------------------------------- */

body {
    font-family: var(--font-sans);
    line-height: var(--lh-base);
    color: var(--color-text);
    background-color: var(--color-bg);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

h1, h2, h3, h4, h5, h6 {
    color: var(--color-text);
    line-height: var(--lh-tight);
}

h1 {
    font-size: 2rem;
    font-weight: 600;
    letter-spacing: -0.02em;
    margin-bottom: var(--space-sm);
}

h2 {
    font-size: 1.3rem;
    font-weight: 600;
    margin-top: var(--space-2xl);
    margin-bottom: var(--space-md);
}

h3 {
    font-size: 1.05rem;
    font-weight: 600;
    margin-top: var(--space-xl);
    margin-bottom: 0.75rem;
}

p {
    margin-bottom: 0.75rem;
}

ul, ol {
    padding-left: var(--space-lg);
    margin-bottom: var(--space-md);
}

li {
    margin-bottom: 0.3rem;
    line-height: var(--lh-loose);
}


/* ---------- 4. Container ----------------------------------------------- */

.container {
    max-width: var(--max-container);
    margin-left: auto;
    margin-right: auto;
    padding-left: var(--space-xl);
    padding-right: var(--space-xl);
}


/* ---------- 5. Card ---------------------------------------------------- */

.card {
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--space-xl);
    background: var(--color-bg);
    box-shadow: var(--shadow-sm);
    transition: box-shadow var(--t-default),
                transform var(--t-default),
                border-color var(--t-default);
    display: flex;
    flex-direction: column;
}

.card:hover {
    border-color: var(--color-border-hover);
    box-shadow: var(--shadow-md);
    transform: translateY(-1px);
}

.card-title {
    font-size: 1.15rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--color-text);
}

.card-text {
    font-size: 0.95rem;
    line-height: var(--lh-loose);
    color: var(--color-text-muted);
    margin-bottom: var(--space-md);
    flex-grow: 1;
}


/* ---------- 6. Grid ---------------------------------------------------- */
/*
   Usage:
     <div class="grid">          — 1 -> 2 columns
     <div class="grid grid-3">   — 1 -> 2 -> 3 columns
*/

.grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--space-lg);
}

@media (min-width: 640px) {
    .grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (min-width: 1024px) {
    .grid-3 {
        grid-template-columns: repeat(3, 1fr);
    }
}


/* ---------- 7. Links & Buttons ----------------------------------------- */

a {
    color: var(--color-link);
    text-decoration: none;
    transition: color var(--t-default);
}

a:hover {
    color: var(--color-link-hover);
    text-decoration: underline;
}

/* Generic button */
.btn {
    display: inline-flex;
    align-items: center;
    gap: var(--space-sm);
    padding: 0.55rem 1.2rem;
    font-size: 0.9rem;
    font-family: inherit;
    font-weight: 500;
    text-decoration: none;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    color: var(--color-text);
    background: var(--color-bg);
    cursor: pointer;
    transition: background-color var(--t-default),
                color var(--t-default),
                border-color var(--t-default),
                box-shadow var(--t-default);
}

.btn:hover {
    background: var(--color-bg-subtle);
    border-color: var(--color-border-hover);
    text-decoration: none;
}

.btn-primary {
    background: var(--color-accent);
    color: #ffffff;
    border-color: var(--color-accent);
}

.btn-primary:hover {
    background: var(--color-accent-hover);
    border-color: var(--color-accent-hover);
    color: #ffffff;
}

.btn-secondary {
    border-color: var(--color-border);
    color: var(--color-text-muted);
    background: transparent;
}

.btn-secondary:hover {
    background: var(--color-bg-subtle);
    color: var(--color-text);
    border-color: var(--color-border-hover);
}


/* ---------- 8. Details / Summary --------------------------------------- */
/*
   Notion-style accordion: clean, no aggressive borders.
   Course-specific CSS (e.g. .task-card details) overrides these.
*/

details {
    margin-top: var(--space-md);
    border-radius: var(--radius-sm);
}

summary {
    cursor: pointer;
    font-size: 0.92rem;
    font-weight: 500;
    color: var(--color-text-muted);
    padding: var(--space-sm) 0;
    transition: color var(--t-default);
    list-style: none;
}

summary::-webkit-details-marker {
    display: none;
}

summary::before {
    content: "\25B8\00a0";
    font-size: 0.8em;
    color: var(--color-text-faint);
    transition: transform var(--t-default);
    display: inline-block;
}

details[open] > summary::before {
    transform: rotate(90deg);
}

summary:hover {
    color: var(--color-text);
}

details[open] > summary {
    margin-bottom: 0.5rem;
    color: var(--color-text);
}


/* ---------- 9. Code / Pre ---------------------------------------------- */

code {
    font-family: var(--font-mono);
    font-size: 0.88em;
    background: var(--color-bg-subtle);
    border: 1px solid var(--color-border);
    padding: 0.12em 0.4em;
    border-radius: 6px;
    color: var(--color-text);
}

pre {
    font-family: var(--font-mono);
    font-size: 0.88rem;
    line-height: 1.55;
    background: var(--color-bg-subtle);
    border: 1px solid var(--color-border);
    padding: var(--space-lg);
    border-radius: var(--radius-md);
    overflow-x: auto;
    margin-bottom: var(--space-lg);
}

/* Reset background for code inside pre (avoid double bg) */
pre code {
    background: none;
    border: none;
    padding: 0;
    font-size: inherit;
    border-radius: 0;
}


/* ---------- 10. Tables ------------------------------------------------- */

table {
    width: 100%;
    border-collapse: collapse;
    margin-bottom: var(--space-lg);
    font-size: 0.9rem;
}

th,
td {
    text-align: left;
    padding: 0.6rem 0.75rem;
    border-bottom: 1px solid var(--color-border);
    line-height: 1.5;
}

th {
    font-weight: 600;
    color: var(--color-text-muted);
    font-size: 0.78rem;
    text-transform: uppercase;
    letter-spacing: 0.04em;
}

/* Zebra striping */
tbody tr:nth-child(even) {
    background: var(--color-bg-subtle);
}

tbody tr:last-child td {
    border-bottom: none;
}


/* ---------- 11. Utility classes ---------------------------------------- */

.muted {
    color: var(--color-text-muted);
    font-size: 0.9rem;
}

.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}


/* ---------- 12. Badge -------------------------------------------------- */

.badge {
    display: inline-block;
    font-size: 0.72rem;
    font-weight: 600;
    padding: 0.15rem 0.5rem;
    border-radius: 6px;
    text-transform: uppercase;
    letter-spacing: 0.04em;
}

.badge-draft {
    color: var(--color-warning);
    background: var(--color-warning-bg);
}

.badge-ready {
    color: var(--color-positive);
    background: var(--color-positive-bg);
}


/* ---------- 13. Callout ------------------------------------------------ */

.callout {
    max-width: var(--max-content);
    margin-bottom: var(--space-xl);
    padding: var(--space-lg) var(--space-xl);
    background: var(--color-bg-subtle);
    border-left: 3px solid var(--color-border);
    border-radius: var(--radius-sm);
}

.callout p {
    font-size: 0.9rem;
    line-height: var(--lh-base);
    color: var(--color-text);
    margin-bottom: 0;
}

.callout-warn {
    border-left-color: rgba(220, 38, 38, 0.35);
    background: rgba(220, 38, 38, 0.04);
}


/* ---------- 14. Footer (minimal) --------------------------------------- */

.footer {
    margin-top: var(--space-3xl);
    padding-top: var(--space-xl);
    border-top: 1px solid var(--color-border);
}


/* ---------- 15. Layout Kit ----------------------------------------------- */
/*
   Reusable layout primitives for page headers, actions, sections.
   Page-specific <style> blocks can override these freely.
*/

/* Hero / page header — constrained width, spacious heading */
.page-header {
    max-width: var(--max-content);
    margin-bottom: var(--space-3xl);
}

.page-header h1 {
    font-size: 2.5rem;
    font-weight: 700;
    letter-spacing: -0.03em;
    line-height: 1.12;
    margin-bottom: var(--space-md);
}

.page-header .subtitle {
    font-size: 1.1rem;
    line-height: var(--lh-loose);
    color: var(--color-text-muted);
}

/* Button row (CTA group below header or section) */
.page-actions {
    display: flex;
    gap: var(--space-sm);
    flex-wrap: wrap;
    margin-top: var(--space-xl);
}

/* Section label — small uppercase with underline */
.section-title {
    font-size: 0.78rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--color-text-faint);
    margin-bottom: var(--space-xl);
    padding-bottom: var(--space-sm);
    border-bottom: 1px solid var(--color-border);
}

/* Kicker — small accent label above headings */
.kicker {
    font-size: 0.78rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--color-accent);
    margin-bottom: var(--space-xs);
}

/* Horizontal divider — thin, soft line */
.divider {
    border: none;
    border-top: 1px solid var(--color-border);
    margin: var(--space-3xl) 0;
}


/* ---------- 16. Top Nav -------------------------------------------------- */
/*
   Thin horizontal bar with site-level links.
   Use: <nav class="top-nav"><a href="/">Главная</a> …</nav>
*/

.top-nav {
    display: flex;
    gap: var(--space-lg);
    flex-wrap: wrap;
    margin-bottom: var(--space-2xl);
    font-size: 0.85rem;
}

.top-nav a {
    color: var(--color-text-faint);
    text-decoration: none;
    transition: color var(--t-default);
}

.top-nav a:hover {
    color: var(--color-text);
    text-decoration: none;
}

.top-nav a.active {
    color: var(--color-text);
    font-weight: 500;
}


/* ---------- 17. List Cards (vertical stack) ------------------------------ */
/*
   Compact vertical card list.
   Use: <div class="list-cards"><a class="list-card" href="…">…</a></div>
*/

.list-cards {
    display: flex;
    flex-direction: column;
    gap: var(--space-sm);
}

.list-card {
    display: block;
    text-decoration: none;
    color: inherit;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--space-lg) var(--space-xl);
    background: var(--color-bg);
    box-shadow: var(--shadow-sm);
    transition: box-shadow var(--t-default),
                transform var(--t-default),
                border-color var(--t-default);
}

.list-card:hover {
    border-color: var(--color-border-hover);
    box-shadow: var(--shadow-md);
    transform: translateY(-1px);
    text-decoration: none;
}

.list-card .card-title {
    font-size: 1.05rem;
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: 0.2rem;
}

.list-card .card-subtitle {
    font-size: 0.9rem;
    color: var(--color-text-muted);
    line-height: 1.55;
}

.list-card .card-meta {
    display: flex;
    gap: var(--space-sm);
    flex-wrap: wrap;
    margin-top: var(--space-sm);
}


/* ---------- 18. Contact Buttons Row -------------------------------------- */

.contact-row {
    display: flex;
    gap: var(--space-sm);
    flex-wrap: wrap;
    align-items: center;
}


/* ---------- 19. Search Input --------------------------------------------- */

.search-input {
    display: block;
    width: 100%;
    padding: var(--space-md) var(--space-xl);
    font-family: inherit;
    font-size: 1rem;
    line-height: 1.5;
    color: var(--color-text);
    background: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    outline: none;
    transition: border-color var(--t-default),
                box-shadow var(--t-default);
}

.search-input::placeholder {
    color: var(--color-text-faint);
}

.search-input:focus {
    border-color: var(--color-accent);
    box-shadow: 0 0 0 3px rgba(0, 113, 227, 0.12);
}


/* ---------- 20. Mark (search highlight) ---------------------------------- */

mark {
    background: rgba(255, 212, 59, 0.28);
    color: inherit;
    padding: 0.05em 0.15em;
    border-radius: 3px;
}


/* ---------- 21. Chips ---------------------------------------------------- */

.chip {
    display: inline-block;
    font-size: 0.7rem;
    font-weight: 600;
    padding: 0.18rem 0.55rem;
    border-radius: 6px;
    background: var(--color-bg-subtle);
    color: var(--color-text-muted);
    border: 1px solid var(--color-border);
    text-transform: lowercase;
    letter-spacing: 0.01em;
    transition: background var(--t-default),
                border-color var(--t-default),
                color var(--t-default);
    cursor: pointer;
}

.chip:hover {
    background: var(--color-bg-muted);
    border-color: var(--color-border-hover);
}

.chip.active {
    background: var(--color-accent);
    color: #fff;
    border-color: var(--color-accent);
}


/* ---------- 22. Top Nav active (enhanced) -------------------------------- */
/*
   Override the plain bold style with a subtle pill background.
*/

.top-nav a.active {
    color: var(--color-text);
    font-weight: 500;
    background: var(--color-bg-muted);
    padding: 0.2rem 0.6rem;
    border-radius: 8px;
    margin: -0.2rem -0.6rem;
}


/* ---------- 23. Site Footer ---------------------------------------------- */

/* ---------- 24. Micro-label ---------------------------------------------- */
/*
   Subtle type-indicator above card titles.
   Use: <div class="micro">Курс</div>
*/

.micro {
    display: inline-block;
    font-size: 0.68rem;
    font-weight: 600;
    letter-spacing: 0.06em;
    text-transform: uppercase;
    color: var(--color-text-faint);
    margin-bottom: 0.4rem;
}


.site-footer {
    margin-top: var(--space-3xl);
    padding-top: var(--space-xl);
    border-top: 1px solid var(--color-border);
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    align-items: baseline;
    gap: var(--space-sm) var(--space-xl);
    font-size: 0.8rem;
    color: var(--color-text-faint);
}

.site-footer a {
    color: var(--color-text-faint);
    text-decoration: none;
    transition: color var(--t-default);
}

.site-footer a:hover {
    color: var(--color-text);
    text-decoration: none;
}

.site-footer-links {
    display: flex;
    gap: var(--space-lg);
    flex-wrap: wrap;
}