/* style.css v4.0 — Ivan Reznikov personal site */
@import url('https://fonts.googleapis.com/css2?family=Instrument+Serif:ital@0;1&display=swap');

:root {
  --font-display:'Instrument Serif',Georgia,serif;
  --font-body:'Satoshi','Inter',system-ui,sans-serif;
  --text-xs:.75rem;--text-sm:.875rem;--text-base:1rem;
  --text-lg:1.125rem;--text-xl:1.25rem;--text-2xl:1.75rem;
  --text-3xl:2.25rem;--text-hero:clamp(2.5rem,6vw,4rem);
  --space-1:.25rem;--space-2:.5rem;--space-3:.75rem;
  --space-4:1rem;--space-5:1.25rem;--space-6:1.5rem;
  --space-8:2rem;--space-10:2.5rem;--space-12:3rem;
  --space-16:4rem;--space-20:5rem;--space-24:6rem;
  --radius-sm:4px;--radius-md:8px;--radius-lg:12px;
  --radius-xl:16px;--radius-2xl:24px;--radius-full:9999px;
  --transition-fast:120ms ease;
  --transition-interactive:200ms cubic-bezier(0.16,1,0.3,1);
  --transition-smooth:400ms cubic-bezier(0.16,1,0.3,1);
  --container-max:1160px;--container-wide:1360px;
  --content-narrow:720px;--header-h:64px;
  --shadow-sm:0 1px 3px oklch(0.2 0.02 250/0.07),0 1px 2px oklch(0.2 0.02 250/0.06);
  --shadow-md:0 4px 16px oklch(0.2 0.02 250/0.10),0 2px 6px oklch(0.2 0.02 250/0.08);
  --shadow-lg:0 10px 40px oklch(0.2 0.02 250/0.14);
  --shadow-xl:0 20px 60px oklch(0.1 0 0/0.4);
}
[data-theme="light"] {
  --color-bg:#F6F5F1;--color-surface:#FFFFFF;
  --color-surface-2:#F9F8F5;--color-surface-offset:#EFEDE8;
  --color-surface-dynamic:#F0EEE9;
  --color-text:#1A1916;--color-text-muted:#5A5750;
  --color-text-faint:#A09D97;--color-text-inverse:#FFFFFF;
  --color-divider:#E5E2DC;--color-primary:#1A7A6E;
  --color-primary-hover:#155F56;
  --color-primary-highlight:color-mix(in oklab,#1A7A6E 10%,transparent);
  --color-gold:#B87333;--color-success:#1A7A6E;--color-error:#C0392B;
}
[data-theme="dark"],:root:not([data-theme="light"]) {
  --color-bg:#111110;--color-surface:#1A1916;
  --color-surface-2:#1F1E1B;--color-surface-offset:#252420;
  --color-surface-dynamic:#2A2925;
  --color-text:#F0EDE6;--color-text-muted:#A09D97;
  --color-text-faint:#6B6862;--color-text-inverse:#111110;
  --color-divider:#2E2C28;--color-primary:#2DB8A8;
  --color-primary-hover:#26A396;
  --color-primary-highlight:color-mix(in oklab,#2DB8A8 12%,transparent);
  --color-gold:#D4956A;--color-success:#2DB8A8;--color-error:#E05C4B;
}
*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth;text-size-adjust:100%;-webkit-text-size-adjust:100%}
body{font-family:var(--font-body);font-size:var(--text-base);line-height:1.6;
  color:var(--color-text);background:var(--color-bg);
  transition:background var(--transition-smooth),color var(--transition-smooth);
  -webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;
  overflow-x:hidden}
img,video{display:block;max-width:100%;height:auto}
button{font:inherit;cursor:pointer;border:none;background:none;color:inherit}
a{color:inherit;text-decoration:none}
ul,ol{list-style:none}
[hidden]{display:none !important}
p{max-width:68ch}
h1,h2,h3,h4,h5,h6{line-height:1.15;font-weight:700}
h1,h2,h3,h4,h5,h6,p{overflow-wrap:break-word}
input,textarea,select{font:inherit;color:inherit}
.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}
.skip-link{position:absolute;top:-100%;left:var(--space-4);z-index:999;padding:var(--space-2) var(--space-4);background:var(--color-primary);color:var(--color-text-inverse);border-radius:var(--radius-md);font-weight:700}
.skip-link:focus{top:var(--space-4)}
.container{max-width:var(--container-max);margin-inline:auto;padding-inline:clamp(var(--space-5),4vw,var(--space-10))}
.container-wide{max-width:var(--container-wide);margin-inline:auto;padding-inline:clamp(var(--space-5),4vw,var(--space-10))}
.section-padded{padding-block:clamp(var(--space-12),6vw,var(--space-20))}

/* HEADER */
.site-header{position:sticky;top:0;z-index:100;height:var(--header-h);
  background:color-mix(in oklab,var(--color-bg) 85%,transparent);
  backdrop-filter:blur(16px) saturate(1.4);-webkit-backdrop-filter:blur(16px) saturate(1.4);
  border-bottom:1px solid transparent;
  transition:border-color var(--transition-fast),box-shadow var(--transition-fast),transform var(--transition-smooth),background var(--transition-smooth)}
.site-header.scrolled{border-color:var(--color-divider);box-shadow:var(--shadow-sm)}
.site-header.hidden{transform:translateY(-100%)}
.header-inner{max-width:var(--container-wide);margin-inline:auto;padding-inline:clamp(var(--space-5),4vw,var(--space-10));height:100%;display:flex;align-items:center;gap:var(--space-8)}
.brand-logo{display:flex;align-items:center;gap:var(--space-3);font-weight:700;font-size:var(--text-base);flex-shrink:0}
.logo-svg{width:32px;height:32px;color:var(--color-primary)}
.brand-name{letter-spacing:-0.01em}
.main-nav{display:flex;align-items:center;gap:var(--space-1);margin-left:auto}
.nav-link{font-size:var(--text-sm);font-weight:500;padding:var(--space-2) var(--space-3);border-radius:var(--radius-md);color:var(--color-text-muted);transition:color var(--transition-fast),background var(--transition-fast)}
.nav-link:hover,.nav-link.active{color:var(--color-text);background:color-mix(in oklab,var(--color-text) 6%,transparent)}
.nav-link.nav-cta{background:var(--color-primary);color:var(--color-text-inverse);padding:var(--space-2) var(--space-4)}
.nav-link.nav-cta:hover{background:var(--color-primary-hover);color:var(--color-text-inverse)}
.header-actions{display:flex;align-items:center;gap:var(--space-2);margin-left:var(--space-4)}
.icon-btn{width:36px;height:36px;display:flex;align-items:center;justify-content:center;border-radius:var(--radius-md);color:var(--color-text-muted);transition:color var(--transition-fast),background var(--transition-fast)}
.icon-btn:hover{color:var(--color-text);background:color-mix(in oklab,var(--color-text) 8%,transparent)}
.hamburger{display:none}
.hamburger svg line{transform-origin:12px 12px;transition:transform var(--transition-fast),opacity var(--transition-fast),x1 var(--transition-fast),x2 var(--transition-fast),y1 var(--transition-fast),y2 var(--transition-fast)}
.nav-close{display:none}
@media(max-width:860px){
  .site-header{background:var(--color-bg);backdrop-filter:none;-webkit-backdrop-filter:none}
  .header-actions{margin-left:auto}
  .hamburger{display:flex}
  .hamburger{background:color-mix(in oklab,var(--color-surface) 94%,transparent);border:1px solid color-mix(in oklab,var(--color-text) 16%,transparent)}
  .hamburger:hover{background:color-mix(in oklab,var(--color-surface-offset) 90%,transparent)}
  .main-nav{position:fixed;inset:0;z-index:90;flex-direction:column;justify-content:center;align-items:flex-start;gap:var(--space-2);padding:var(--space-12) var(--space-8);background:var(--color-bg);transform:translateX(100%);transition:transform var(--transition-smooth);margin-left:0}
  .main-nav.open{transform:none}
  .nav-close{display:inline-flex;position:absolute;top:calc(var(--header-h) + var(--space-2));right:var(--space-4);width:42px;height:42px;border-radius:var(--radius-full);align-items:center;justify-content:center;border:1px solid color-mix(in oklab,var(--color-text) 18%,transparent);background:color-mix(in oklab,var(--color-surface) 94%,transparent);font-size:1.6rem;line-height:1;color:var(--color-text-muted)}
  .nav-close:hover{color:var(--color-text);background:color-mix(in oklab,var(--color-surface-offset) 90%,transparent)}
  .nav-link{font-size:var(--text-xl);padding:var(--space-3) var(--space-4);width:100%}
  .nav-link.nav-cta{display:inline-flex;width:auto;margin-top:var(--space-4)}
}

/* FOOTER */
.site-footer{padding-block:var(--space-16);border-top:1px solid var(--color-divider);background:var(--color-surface)}
.footer-inner{display:grid;grid-template-columns:1fr auto 1fr;align-items:center;gap:var(--space-8)}
.footer-brand{display:grid;gap:var(--space-2)}
.footer-tagline{font-size:var(--text-xs);color:var(--color-text-faint);letter-spacing:.08em;text-transform:uppercase;white-space:nowrap}
.footer-nav{display:flex;flex-wrap:wrap;gap:var(--space-1);justify-content:center}
.footer-nav a{font-size:var(--text-sm);color:var(--color-text-faint);padding:var(--space-1) var(--space-2);border-radius:var(--radius-sm);transition:color var(--transition-fast)}
.footer-nav a:hover{color:var(--color-primary)}
.footer-copy{font-size:var(--text-xs);color:var(--color-text-faint);text-align:right}
@media(max-width:700px){.footer-inner{grid-template-columns:1fr;text-align:center;gap:var(--space-5)}.footer-brand{justify-items:center}.footer-nav{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:var(--space-2);width:100%}.footer-nav a{padding:var(--space-2) var(--space-2);border:1px solid color-mix(in oklab,var(--color-text) 10%,transparent);background:color-mix(in oklab,var(--color-surface-2) 80%,transparent)}.footer-copy{text-align:center}}

/* BUTTONS */
.btn{display:inline-flex;align-items:center;gap:var(--space-2);padding:.65rem 1.25rem;border-radius:var(--radius-full);font-size:var(--text-sm);font-weight:700;text-decoration:none;transition:all var(--transition-interactive);white-space:nowrap;cursor:pointer;border:1.5px solid transparent}
.btn-lg{padding:.85rem 1.75rem;font-size:var(--text-base)}
.btn-sm{padding:.45rem 1rem;font-size:var(--text-sm)}
.btn-primary{background:var(--color-primary);color:var(--color-text-inverse)}
.btn-primary:hover{background:var(--color-primary-hover);transform:translateY(-1px);box-shadow:0 4px 14px color-mix(in oklab,var(--color-primary) 30%,transparent)}
.btn-secondary{background:transparent;color:var(--color-text);border-color:color-mix(in oklab,var(--color-text) 20%,transparent)}
.btn-secondary:hover{background:color-mix(in oklab,var(--color-text) 6%,transparent);transform:translateY(-1px)}
.btn-ghost{background:transparent;color:var(--color-text-muted)}
.btn-ghost:hover{color:var(--color-text);background:color-mix(in oklab,var(--color-text) 5%,transparent)}

/* BADGES */
.badge{display:inline-flex;align-items:center;gap:var(--space-1);font-size:var(--text-xs);font-weight:700;padding:.2rem .7rem;border-radius:var(--radius-full);white-space:nowrap}
.badge-primary{background:color-mix(in oklab,var(--color-primary) 12%,transparent);color:var(--color-primary);border:1px solid color-mix(in oklab,var(--color-primary) 22%,transparent)}
.badge-warm{background:color-mix(in oklab,var(--color-gold) 12%,transparent);color:var(--color-gold);border:1px solid color-mix(in oklab,var(--color-gold) 22%,transparent)}
.badge-green{background:color-mix(in oklab,var(--color-success) 12%,transparent);color:var(--color-success);border:1px solid color-mix(in oklab,var(--color-success) 22%,transparent)}
.badge-neutral{background:color-mix(in oklab,var(--color-text-faint) 12%,transparent);color:var(--color-text-muted);border:1px solid color-mix(in oklab,var(--color-text-faint) 18%,transparent)}
.badge-health{background:color-mix(in oklab,#2DB8A8 14%,transparent);color:#2DB8A8;border:1px solid color-mix(in oklab,#2DB8A8 30%,transparent)}
.badge-llm{background:color-mix(in oklab,#8C8A84 16%,transparent);color:color-mix(in oklab,var(--color-text) 70%,#8C8A84 30%);border:1px solid color-mix(in oklab,#8C8A84 28%,transparent)}
.badge-graph{background:color-mix(in oklab,#3F7CAC 14%,transparent);color:#3F7CAC;border:1px solid color-mix(in oklab,#3F7CAC 30%,transparent)}
.badge-life{background:color-mix(in oklab,#4FAF5A 14%,transparent);color:#4FAF5A;border:1px solid color-mix(in oklab,#4FAF5A 30%,transparent)}
.badge-data{background:color-mix(in oklab,#2D6CDF 14%,transparent);color:#2D6CDF;border:1px solid color-mix(in oklab,#2D6CDF 30%,transparent)}
.badge-ml{background:color-mix(in oklab,#C86B2A 14%,transparent);color:#C86B2A;border:1px solid color-mix(in oklab,#C86B2A 30%,transparent)}

/* TYPOGRAPHY */
.section-header{margin-bottom:var(--space-10)}
.section-header h2{font-family:var(--font-display);font-size:var(--text-3xl);font-weight:400;margin-top:var(--space-2)}
.eyebrow{font-size:var(--text-xs);font-weight:800;text-transform:uppercase;letter-spacing:.15em;color:var(--color-primary)}
.page-title{font-family:var(--font-display);font-size:clamp(2.2rem,5vw,3.5rem);font-weight:400;line-height:1.0}
.page-lead{font-size:var(--text-lg);color:var(--color-text-muted);max-width:52ch;line-height:1.6}

/* ANIMATIONS */
.fade-up{animation:fadeUp 500ms cubic-bezier(0.16,1,0.3,1) both;animation-delay:var(--delay,0ms)}
@keyframes fadeUp{from{opacity:0;transform:translateY(14px)}to{opacity:1;transform:none}}
@media(prefers-reduced-motion:reduce){.fade-up,.scroll-reveal{animation:none!important;opacity:1!important;transform:none!important}}
@supports(animation-timeline:view()){
  .scroll-reveal{animation:fadeUp 500ms cubic-bezier(0.16,1,0.3,1) both;animation-timeline:view();animation-range:entry 0% entry 30%;animation-delay:var(--card-delay,0ms)}
}

/* AVAILABILITY BADGE */
.availability-badge{display:flex;align-items:center;gap:var(--space-2);font-size:var(--text-sm);font-weight:500;color:var(--color-text-muted);padding:var(--space-3) var(--space-4);border-radius:var(--radius-full);background:color-mix(in oklab,var(--color-success) 8%,var(--color-surface));border:1px solid color-mix(in oklab,var(--color-success) 20%,transparent);width:fit-content}
.badge-dot{width:8px;height:8px;background:var(--color-success);border-radius:50%;flex-shrink:0;animation:pulse 2s infinite}
@keyframes pulse{0%,100%{opacity:1;transform:scale(1)}50%{opacity:.5;transform:scale(1.3)}}

/* CTA BLOCK */
.cta-block{display:flex;align-items:center;justify-content:space-between;gap:var(--space-12);flex-wrap:wrap;padding:var(--space-12);background:color-mix(in oklab,var(--color-primary) 5%,var(--color-surface));border:1px solid color-mix(in oklab,var(--color-primary) 15%,transparent);border-radius:var(--radius-2xl)}
.cta-text{display:grid;gap:var(--space-3)}
.cta-text h2{font-family:var(--font-display);font-size:var(--text-2xl);font-weight:400}
.cta-text p{color:var(--color-text-muted);max-width:44ch}
.cta-actions{display:flex;flex-wrap:wrap;gap:var(--space-3)}
@media(max-width:700px){.cta-block{flex-direction:column;align-items:flex-start;padding:var(--space-8)}}

/* FORM FIELDS */
.form-field{display:grid;gap:var(--space-2)}
.form-field label{font-size:var(--text-xs);font-weight:700;text-transform:uppercase;letter-spacing:.12em;color:var(--color-text-muted)}
.label-optional{font-weight:400;text-transform:none;letter-spacing:0}
.form-field input,.form-field textarea,.form-field select{min-height:48px;padding:.85rem 1rem;background:color-mix(in oklab,var(--color-surface) 96%,transparent);border:1.5px solid color-mix(in oklab,var(--color-text) 14%,transparent);border-radius:var(--radius-md);font-size:var(--text-base);transition:border-color var(--transition-interactive),box-shadow var(--transition-interactive)}
.form-field input:focus,.form-field textarea:focus,.form-field select:focus{outline:none;border-color:var(--color-primary);box-shadow:0 0 0 3px color-mix(in oklab,var(--color-primary) 14%,transparent)}
.form-field input::placeholder,.form-field textarea::placeholder{color:var(--color-text-faint)}
.form-field input[aria-invalid="true"],.form-field textarea[aria-invalid="true"]{border-color:var(--color-error)}
.form-field textarea{resize:vertical;min-height:130px;line-height:1.6}
.field-error{font-size:var(--text-xs);color:var(--color-error);min-height:1em}

/* FILTER BUTTONS */
.filter-btn{padding:var(--space-2) var(--space-4);border-radius:var(--radius-full);font-size:var(--text-sm);font-weight:500;background:color-mix(in oklab,var(--color-surface-offset) 60%,transparent);border:1.5px solid transparent;color:var(--color-text-muted);transition:all var(--transition-interactive)}
.filter-btn:hover{background:color-mix(in oklab,var(--color-surface-dynamic) 80%,transparent);color:var(--color-text)}
.filter-btn.active{background:var(--color-primary);color:var(--color-text-inverse);border-color:var(--color-primary)}

/* TEXT LINK */
.text-link{color:var(--color-primary);text-decoration:underline;text-underline-offset:3px}

/* RESPONSIVE GLOBAL */
@media(max-width:700px){
  :root{--header-h:60px}
  .container,.container-wide{padding-inline:var(--space-4)}
  .section-padded{padding-block:clamp(var(--space-12),11vw,var(--space-16))}
  .header-inner{padding-inline:var(--space-4);gap:var(--space-4)}
  .brand-name{font-size:var(--text-sm)}
  .main-nav{padding:calc(var(--header-h) + var(--space-6)) var(--space-5) var(--space-8)}
  .page-lead{font-size:var(--text-base)}
  .form-row{grid-template-columns:1fr!important}
  .talks-stats-bar{flex-wrap:wrap;width:auto}
}
@media(max-width:560px){
  .header-actions{margin-left:auto;gap:var(--space-1)}
  .icon-btn{width:40px;height:40px}
  .main-nav{padding:calc(var(--header-h) + var(--space-4)) var(--space-4) var(--space-6)}
  .nav-close{right:var(--space-3)}
  .nav-link{font-size:var(--text-lg);padding:var(--space-3)}
  .footer-nav{grid-template-columns:1fr}
  .footer-tagline{white-space:normal}
}
@media(max-width:380px){
  :root{--header-h:56px}
  .header-inner{gap:var(--space-2)}
  .brand-logo{gap:var(--space-2)}
  .brand-name{font-size:var(--text-xs)}
  .main-nav{padding:calc(var(--header-h) + var(--space-3)) var(--space-3) var(--space-5)}
  .nav-close{top:calc(var(--header-h) + var(--space-1));right:var(--space-2);width:38px;height:38px;font-size:1.35rem}
  .nav-link{font-size:var(--text-base);padding:var(--space-2) var(--space-2)}
  .site-footer{padding-block:var(--space-12)}
  .footer-nav a{font-size:var(--text-xs)}
}