:root{
  --container: 1440px;
  --pad: 18px;

  --text:#111;
  --muted: rgba(17,17,17,.72);
  --bg:#fff;
  --border: rgba(0,0,0,.10);

  --r-md: 14px;
  --r-lg: 18px;

  --shadow: 0 12px 30px rgba(0,0,0,.10);

  --s-1: 6px;
  --s-2: 10px;
  --s-3: 14px;
  --s-4: 18px;
  --s-5: 24px;
  --s-6: 32px;
  --s-7: 44px;
}

*{ box-sizing: border-box; }

html, body {
  margin: 0;
  font-family: "Inter", system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  font-size: 16.5px;
  line-height: 1.55;
}

a{ color:inherit; text-decoration:none; }
p{ margin:0 0 var(--s-4); color:var(--muted); }

/* Titres – typographie unifiée (non Nature) */
h1, h2, h3, h4{
  font-family: "Inter", system-ui, sans-serif;
  font-weight: 700;
  letter-spacing: -0.015em;
  margin: 0 0 var(--s-3);
  line-height: 1.2;
}

/* Hiérarchie des tailles */
h1{
  font-size: clamp(30px, 3.2vw, 44px);
  font-weight: 800;
}

h2{
  font-size: clamp(22px, 2.4vw, 30px);
}

h3{
  font-size: 18px;
  font-weight: 600;
}

h4{
  font-size: 15px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

small{ color:var(--muted); }
.container{ width:min(var(--container), 100%); 
  margin:0 auto; 
  padding:0 var(--pad); }

/* Container extra-large (header, hero, large sections) */
.container-xl{
  width: min(1680px, 100%);
  margin: 0 auto;
  padding: 0 var(--pad);
}
/* Header */
.site-header{
  position: sticky;
  top: 0;
  z-index: 1000;
  background: rgba(255,255,255,.92);
  backdrop-filter: blur(8px);
  border-bottom:1px solid var(--border);
}
.header-row{
  display:flex;
  align-items:center;
  gap:14px;
  padding: 12px 0;
}

/* Logo YS2C – légèrement plus présent */
.brand-logo{
  height: 48px;        /* desktop */
  width: auto;
  max-width: 160px;
  display: block;
}

/* Tablet */
@media (max-width: 1024px){
  .brand-logo{
    height: 42px;
    max-width: 145px;
  }
}

/* Mobile */
@media (max-width: 600px){
  .brand-logo{
    height: 36px;
    max-width: 120px;
  }
}

/* Desktop nav */
.nav-desktop{
  margin-left:auto;
  display:none;
  align-items:center;
  gap: 16px;
}
.nav-desktop a{
  padding: 8px 10px;
  border-radius: 12px;
  font-weight: 600;
  opacity: .9;
}
.nav-desktop a:hover{ background: rgba(0,0,0,.05); }

.btn-primary{
  margin-left: 6px;
  padding: 9px 14px;
  border-radius: 14px;
  background:#111;
  color:#fff;
  border:1px solid #111;
  font-weight: 700;
}

/* Dropdown desktop (CSS only) */
.nav-dd{ position:relative; }
.nav-dd-btn{
  padding: 8px 10px;
  border-radius: 12px;
  font-weight: 600;
  opacity: .9;
  cursor: default;
}
.nav-dd:hover .nav-dd-menu{ display:block; }

.nav-dd-menu{
  position:absolute;
  right:0;
  top: calc(100% + 10px);
  background:#fff;
  border:1px solid var(--border);
  border-radius: var(--r-lg);
  box-shadow: var(--shadow);
  padding: 8px;
  min-width: 220px;
  display:none;
}

.nav-dd-menu a{
  display:block;
  padding: 10px 10px;
  border-radius: var(--r-md);
  font-weight: 600;
  opacity: .9;
}

.nav-dd:focus-within .nav-dd-menu{ display:block; }

.nav-dd-menu a:hover{ background: rgba(0,0,0,.06); }

/* Mobile menu (no JS) via details */
.nav-details{ margin-left:auto; position:relative; display:block; }
.nav-summary{
  list-style:none;
  width:44px; height:40px;
  border-radius: 14px;
  border:1px solid var(--border);
  background:#fff;
  display:flex; align-items:center; justify-content:center;
  cursor:pointer;
}
.nav-summary::-webkit-details-marker{ display:none; }
.burger{ width:18px; height:2px; background:#111; position:relative; display:block; }
.burger:before,.burger:after{ content:""; position:absolute; left:0; width:18px; height:2px; background:#111; }
.burger:before{ top:-6px; }
.burger:after{ top:6px; }

.nav-panel{
  position:absolute;
  right:0;
  top: calc(100% + 10px);
  width: min(92vw, 360px);
  background:#fff;
  border:1px solid var(--border);
  border-radius: var(--r-lg);
  box-shadow: var(--shadow);
  padding: 10px;
  display:flex;
  flex-direction:column;
  gap: 6px;
}
.nav-panel a{
  padding: 10px 10px;
  border-radius: var(--r-md);
  font-weight: 650;
  opacity: .9;
}
.nav-panel a:hover{ background: rgba(0,0,0,.06); }
.nav-panel .nav-cta{
  margin-top: 6px;
  background:#111;
  color:#fff;
  border:1px solid #111;
}

.nav-group{
  margin-top: 6px;
  padding-top: 10px;
  border-top: 1px solid var(--border);
}
.nav-group-title{
  display:block;
  padding: 6px 10px;
  font-weight: 800;
  opacity: .7;
  text-transform: uppercase;
  font-size: 12px;
  letter-spacing: .06em;
}

/* Switch desktop/tablet */
@media (min-width: 920px){
  .nav-desktop{ display:flex; }
  .nav-details{ display:none; }
}

/* Page blocks */
.hero{
  padding: var(--s-7) 0 var(--s-6);
  border-bottom:1px solid var(--border);
}
.hero p{ max-width: 70ch; }

.grid{
  display:grid;
  grid-template-columns: 1fr;
  gap: var(--s-4);
}

@media (min-width: 700px){
  .grid{ grid-template-columns: repeat(2, 1fr); }
}

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

.card{
  border:1px solid var(--border);
  border-radius: var(--r-lg);
  padding: var(--s-5);
  background:#fff;
}
.card h3{ margin-bottom: var(--s-2); }
.card p{ margin:0; }

.card ul{
  margin: 0;
  padding-left: 18px;
  color: var(--muted);
}

.card li{ margin: 8px 0; }

/* At a glance */
.facts{
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: var(--s-4);
  margin: var(--s-6) 0 var(--s-7);
}

.facts div{
  border: 1px solid var(--border);
  border-radius: var(--r-lg);
  padding: 14px 16px;
  background: #fff;
  font-size: 14px;
}

.facts strong{
  font-weight: 700;
  font-size: 13px;
  text-transform: uppercase;
  letter-spacing: .05em;
  opacity: .75;
}

/* footer */
.footer{
  border-top:1px solid var(--border);
  padding: var(--s-6) 0;
  margin-top: var(--s-7);
}
.footer-grid{
  display:grid;
  grid-template-columns: 1fr;
  gap: var(--s-4);
}

.footer h3{
  font-size: 15px;
  text-transform: uppercase;
  letter-spacing: .08em;
  opacity: .8;
}

.footer a{
  text-decoration: none;
}

.footer a:hover{
  text-decoration: underline;
  text-underline-offset: 3px;
}

.footer-credit{
  font-size: 12px;
  color: var(--muted);
  margin-top: var(--s-4);
}

@media (min-width: 900px){
  .footer-grid{ grid-template-columns: 2fr 1fr 1fr; }
}

/* Partners / Sponsors strip */
.partners-strip{
  width: 100%;
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
  background: #fafafa;
  overflow: hidden;
  padding: 22px 0;
  margin-top: var(--s-7);
}

.partners-marquee{
  overflow: hidden;
  width: 100%;
}

.partners-track{
  display: flex;
  width: max-content;
  animation: partners-scroll 40s linear infinite;
}

.partners-group{
  display: flex;
  align-items: center;
  gap: 56px;
  padding-right: 56px;     /* évite un “collage” entre fin et début */
  flex-shrink: 0;          /* CRITIQUE: empêche le groupe de se compresser */
}

.partners-group img{
  height: 48px;
  width: auto;
  opacity: 1;
  filter: none;
  background: #fff;
  padding: 6px 10px;
  border-radius: 12px;
  border: 1px solid rgba(0,0,0,.06);
}

@keyframes partners-scroll{
  from { transform: translateX(0); }
  to   { transform: translateX(-50%); }
}

/* Pause au survol (optionnel) */
.partners-strip:hover .partners-track{
  animation-play-state: paused;
}

/* Accessibilité: réduire le mouvement si demandé */
@media (prefers-reduced-motion: reduce){
  .partners-track{ animation: none; }
}

/* Sponsor placeholder */
.partner-placeholder{
  height: 48px;
  min-width: 150px;
  padding: 6px 14px;
  border-radius: 12px;
  border: 2px dashed rgba(0,0,0,.25);
  background: #fff;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  text-align: center;
  cursor: pointer;
  transition: border-color .2s ease, background .2s ease, transform .2s ease;
}

.partner-placeholder span{
  font-weight: 700;
  font-size: 13px;
}

.partner-placeholder small{
  font-size: 11px;
  color: var(--muted);
}

.partner-placeholder:hover{
  border-color: #111;
  background: rgba(0,0,0,.03);
  transform: translateY(-1px);
}



/* Pause on hover (desktop) */
.partners-strip:hover .partners-row{
  animation-play-state: paused;
}

@keyframes partners-scroll{
  from{
    transform: translateX(0);
  }
  to{
    transform: translateX(-50%);
  }
}

/* === Photo marquee (Conference) === */
.photo-strip{
  margin: 10px 0 28px;
}

.photo-marquee{
  overflow: hidden;
  border-radius: 16px;
  background: rgba(0,0,0,0.04);
  padding: 10px;
}

.photo-track{
  display: flex;
  gap: 14px;
  width: max-content;
  animation: photoScroll 38s linear infinite;
  will-change: transform;
}

.photo-group{
  display: flex;
  gap: 14px;
}

.photo-group img{
  height: 170px;
  width: 260px;
  object-fit: cover;
  border-radius: 14px;
  display: block;
}

/* Pause on hover (nice UX) */
.photo-marquee:hover .photo-track{
  animation-play-state: paused;
}

@keyframes photoScroll{
  from { transform: translateX(0); }
  to   { transform: translateX(-50%); }
}

/* Mobile */
@media (max-width: 700px){
  .photo-group img{
    height: 140px;
    width: 220px;
  }
}

.clean-list{
  margin: 0;
  padding-left: 18px;
  color: var(--muted);
}
.clean-list li{ margin: 8px 0; }