/* The Thread — AI through the product journey */

.thread-hero {
  padding: 10rem var(--gutter) 4rem;
  background: var(--cream-light);
  text-align: center;
}
.thread-hero-inner {
  max-width: 760px;
  margin: 0 auto;
}
.thread-hero h1 {
  font-family: var(--font-serif);
  font-style: italic;
  font-size: clamp(3rem, 6.5vw, 5rem);
  font-weight: 400;
  line-height: 1.05;
  margin: 1rem 0 1.5rem;
  color: var(--ink);
}
.thread-hero p.lead {
  font-size: 1.125rem;
  color: var(--ink);
  line-height: 1.7;
  max-width: 580px;
  margin: 0 auto;
}
.thread-hero .eyebrow {
  font-family: var(--font-sans);
  font-size: 0.75rem;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--accent);
}

/* The boundary callout — what AI does not do */
.thread-boundary {
  max-width: 760px;
  margin: 3.5rem auto 0;
  padding: 2rem 2.25rem;
  border: 1px solid var(--line);
  background: rgba(255,255,255,0.5);
}
.thread-boundary-title {
  font-family: var(--font-serif);
  font-style: italic;
  font-size: 1.25rem;
  color: var(--accent);
  margin: 0 0 1rem;
}
.thread-boundary ul {
  list-style: none;
  padding: 0;
  margin: 0;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.5rem 2rem;
}
.thread-boundary ul li {
  font-family: var(--font-sans);
  font-size: 0.875rem;
  color: var(--ink);
  line-height: 1.5;
  padding-left: 1.25rem;
  position: relative;
}
.thread-boundary ul li::before {
  content: "—";
  position: absolute;
  left: 0;
  color: var(--accent);
}

/* 5 phases */
.thread-phases {
  max-width: 1100px;
  margin: 5rem auto 0;
  padding: 0 var(--gutter);
}
.thread-phases-grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 1.5rem;
  position: relative;
}
.thread-phases-grid::before {
  content: "";
  position: absolute;
  top: 28px;
  left: calc(10% + 10px);
  right: calc(10% + 10px);
  height: 1px;
  background: var(--line);
  z-index: 0;
}
.thread-phase {
  text-align: center;
  position: relative;
  z-index: 1;
}
.thread-phase-dot {
  width: 56px;
  height: 56px;
  border-radius: 50%;
  background: var(--cream-light);
  border: 1px solid var(--accent);
  margin: 0 auto 1.25rem;
  display: grid;
  place-items: center;
  font-family: var(--font-serif);
  font-style: italic;
  font-size: 1.5rem;
  color: var(--accent);
}
.thread-phase h3 {
  font-family: var(--font-serif);
  font-style: italic;
  font-size: 1.5rem;
  font-weight: 400;
  margin: 0 0 0.75rem;
  color: var(--ink);
}
.thread-phase .phase-eyebrow {
  font-family: var(--font-sans);
  font-size: 0.68rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--muted);
  display: block;
  margin-bottom: 0.5rem;
}
.thread-phase p {
  font-size: 0.95rem;
  line-height: 1.6;
  color: var(--ink);
  margin: 0 0 1rem;
}
.thread-phase .ai-does {
  font-family: var(--font-sans);
  font-size: 0.78rem;
  color: var(--accent);
  font-weight: 500;
  letter-spacing: 0.04em;
  margin-bottom: 0.4rem;
  display: block;
}

/* Chat surface */
.thread-chat {
  max-width: 820px;
  margin: 6rem auto 0;
  padding: 0 var(--gutter);
}
.thread-chat-intro {
  text-align: center;
  margin-bottom: 2.5rem;
}
.thread-chat-intro h2 {
  font-family: var(--font-serif);
  font-style: italic;
  font-size: clamp(2rem, 4vw, 2.75rem);
  font-weight: 400;
  margin: 0 0 1rem;
  color: var(--ink);
}
.thread-chat-intro p {
  color: var(--muted);
  font-size: 1rem;
}
.thread-chat-card {
  background: var(--cream-light);
  border: 1px solid var(--line);
  padding: 2rem;
}
.thread-phase-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-bottom: 1.5rem;
}
.thread-phase-tab {
  background: transparent;
  border: 1px solid var(--line);
  color: var(--ink);
  font-family: var(--font-sans);
  font-size: 0.78rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  padding: 0.6rem 1rem;
  cursor: pointer;
  transition: border-color 0.2s, color 0.2s, background 0.2s;
}
.thread-phase-tab:hover {
  border-color: var(--accent);
  color: var(--accent);
}
.thread-phase-tab.active {
  background: var(--ink);
  color: var(--cream-light);
  border-color: var(--ink);
}
.thread-chat-log {
  min-height: 200px;
  max-height: 480px;
  overflow-y: auto;
  padding: 1.25rem;
  background: #fff;
  border: 1px solid var(--line);
  margin-bottom: 1rem;
  font-size: 0.95rem;
  line-height: 1.7;
  color: var(--ink);
}
.thread-msg {
  margin-bottom: 1.25rem;
  padding: 0.75rem 1rem;
  border-radius: 6px;
}
.thread-msg.user {
  background: var(--tan);
  color: var(--ink);
  margin-left: 2.5rem;
}
.thread-msg.assistant {
  background: rgba(196, 161, 138, 0.12);
  border-left: 2px solid var(--accent);
  margin-right: 2.5rem;
}
.thread-msg.system {
  font-style: italic;
  color: var(--muted);
  font-size: 0.88rem;
  text-align: center;
  background: none;
  padding: 0.5rem 0;
}
.thread-msg-label {
  font-family: var(--font-sans);
  font-size: 0.68rem;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 0.4rem;
  display: block;
}
.thread-msg.user .thread-msg-label { color: var(--ink); }
.thread-chat-input-row {
  display: flex;
  gap: 0.5rem;
}
.thread-chat-input {
  flex: 1;
  padding: 0.85rem 1rem;
  border: 1px solid var(--line);
  background: #fff;
  font-family: inherit;
  font-size: 0.95rem;
  color: var(--ink);
  resize: vertical;
  min-height: 56px;
  max-height: 200px;
  border-radius: 0;
}
.thread-chat-input:focus {
  outline: none;
  border-color: var(--accent);
}
.thread-chat-send {
  background: var(--ink);
  color: var(--cream-light);
  border: none;
  padding: 0 1.5rem;
  font-family: var(--font-sans);
  font-size: 0.85rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  cursor: pointer;
  white-space: nowrap;
}
.thread-chat-send:hover { background: var(--accent); }
.thread-chat-send:disabled { opacity: 0.4; cursor: not-allowed; }

.thread-chat-meta {
  margin-top: 1rem;
  font-family: var(--font-sans);
  font-size: 0.72rem;
  letter-spacing: 0.05em;
  color: var(--muted);
  text-align: center;
}

/* Closing */
.thread-closing {
  background: var(--ink);
  color: var(--cream-light);
  padding: 5rem var(--gutter);
  text-align: center;
  margin-top: 6rem;
}
.thread-closing-inner {
  max-width: 640px;
  margin: 0 auto;
}
.thread-closing h2 {
  font-family: var(--font-serif);
  font-style: italic;
  font-size: clamp(2rem, 4vw, 2.75rem);
  color: var(--cream-light);
  margin: 0 0 1rem;
}
.thread-closing p {
  color: var(--tan);
  line-height: 1.8;
  font-size: 1rem;
  margin-bottom: 1rem;
}
.thread-closing em {
  font-family: var(--font-serif);
  font-style: italic;
}

@media (max-width: 880px) {
  .thread-phases-grid {
    grid-template-columns: 1fr 1fr;
    gap: 2.5rem 1.5rem;
  }
  .thread-phases-grid::before { display: none; }
  .thread-boundary ul { grid-template-columns: 1fr; }
}
@media (max-width: 520px) {
  .thread-phases-grid { grid-template-columns: 1fr; }
  .thread-msg.user { margin-left: 1rem; }
  .thread-msg.assistant { margin-right: 1rem; }
}