/* ==========================================================================
   HowItWorks — base stylesheet (public site + shared tokens)
   ========================================================================== */

:root {
  /* Palette */
  --bg:          #080b16;
  --bg-2:        #0d1225;
  --surface:     #131a30;
  --surface-2:   #1a2340;
  --border:      rgba(255, 255, 255, .07);
  --border-2:    rgba(255, 255, 255, .12);
  --fg:          #eef1f8;
  --fg-dim:      #a3acc4;
  --muted:       #6b7590;
  --accent:      #ffb300;   /* energy */
  --flow:        #4fc3f7;   /* current */
  --ok:          #55d187;
  --warn:        #ffb84d;
  --danger:      #ff6b6b;

  /* Tier colours */
  --tier-toddler:  #ffb3c7;
  --tier-children: #ffb84d;
  --tier-eli5:     #7ee787;
  --tier-teens:    #4fc3f7;
  --tier-adults:   #b39ddb;

  /* Radii + shadow */
  --radius:      12px;
  --radius-sm:   8px;
  --radius-lg:   20px;
  --shadow:      0 8px 32px rgba(0, 0, 0, .35);
  --shadow-sm:   0 2px 8px rgba(0, 0, 0, .25);

  /* Typography */
  --font: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --mono: ui-monospace, "SF Mono", Menlo, Consolas, monospace;
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  font-family: var(--font);
  font-size: 16px;
  line-height: 1.55;
  color: var(--fg);
  background: var(--bg);
  background-image:
    radial-gradient(900px 500px at 10% -10%, rgba(79, 195, 247, .06), transparent 60%),
    radial-gradient(800px 500px at 110% 10%, rgba(255, 179, 0, .05), transparent 60%);
  background-attachment: fixed;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* ---- Typography ---- */
h1, h2, h3, h4 { margin: 0 0 .5rem; line-height: 1.2; letter-spacing: -.01em; }
h1 { font-size: clamp(1.6rem, 3vw, 2.2rem); font-weight: 700; }
h2 { font-size: 1.25rem; font-weight: 650; }
h3 { font-size: 1rem; font-weight: 600; }
p  { margin: 0 0 1rem; color: var(--fg-dim); }

a { color: var(--flow); text-decoration: none; transition: color .15s; }
a:hover { color: #7ed4fb; }

code, kbd, pre {
  font-family: var(--mono);
  font-size: .9em;
  background: rgba(255, 255, 255, .06);
  padding: .1em .4em;
  border-radius: 5px;
  color: #d6def0;
}

pre code { padding: 0; background: none; }

/* ---- Layout ---- */
main { flex: 1; }

.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 2rem 1.5rem 4rem;
}

/* ---- Top navigation ---- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: .9rem 1.5rem;
  background: rgba(8, 11, 22, .8);
  backdrop-filter: saturate(160%) blur(10px);
  -webkit-backdrop-filter: saturate(160%) blur(10px);
  border-bottom: 1px solid var(--border);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: .6rem;
  font-weight: 700;
  font-size: 1.05rem;
  letter-spacing: -.01em;
  color: var(--fg);
}
.brand:hover { color: var(--fg); }
.brand-mark {
  width: 26px; height: 26px;
  border-radius: 8px;
  background: conic-gradient(from 210deg, var(--accent), var(--flow), var(--accent));
  box-shadow: 0 0 18px rgba(255, 179, 0, .35), inset 0 0 8px rgba(0,0,0,.4);
}

.site-nav {
  display: flex;
  align-items: center;
  gap: 1.25rem;
  font-size: .9rem;
}
.site-nav a {
  color: var(--fg-dim);
  font-weight: 500;
}
.site-nav a:hover, .site-nav a.active { color: var(--fg); }

/* ---- Buttons ---- */
button, .btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: .5rem;
  padding: .55rem 1rem;
  font-family: inherit;
  font-size: .9rem;
  font-weight: 600;
  line-height: 1;
  border: 1px solid transparent;
  border-radius: var(--radius-sm);
  background: var(--accent);
  color: #14100a;
  cursor: pointer;
  text-decoration: none;
  transition: transform .06s ease, filter .15s ease, background .15s;
}
button:hover, .btn:hover { filter: brightness(1.06); color: #14100a; }
button:active, .btn:active { transform: translateY(1px); }

.btn-secondary {
  background: transparent;
  color: var(--fg);
  border-color: var(--border-2);
}
.btn-secondary:hover { background: rgba(255,255,255,.04); color: var(--fg); }

.btn-danger {
  background: transparent;
  color: var(--danger);
  border-color: rgba(255, 107, 107, .4);
}
.btn-danger:hover { background: rgba(255, 107, 107, .08); color: var(--danger); }

.btn-ghost {
  background: transparent;
  color: var(--fg-dim);
  padding: .35rem .6rem;
}
.btn-ghost:hover { color: var(--fg); background: rgba(255,255,255,.05); }

/* ---- Form controls ---- */
input, textarea, select {
  font-family: inherit;
  font-size: .95rem;
  color: var(--fg);
  background: rgba(0, 0, 0, .28);
  border: 1px solid var(--border-2);
  border-radius: var(--radius-sm);
  padding: .6rem .75rem;
  width: 100%;
  transition: border-color .15s, box-shadow .15s;
}
input:focus, textarea:focus, select:focus {
  outline: none;
  border-color: var(--flow);
  box-shadow: 0 0 0 3px rgba(79, 195, 247, .18);
}
label {
  display: block;
  font-size: .85rem;
  color: var(--fg-dim);
  font-weight: 500;
  margin-bottom: .35rem;
}
.field { margin-bottom: 1rem; }

/* ---- Cards ---- */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem;
  transition: transform .15s ease, border-color .15s, box-shadow .2s;
}
.card:hover {
  border-color: var(--border-2);
  box-shadow: var(--shadow-sm);
}

/* ---- Flash messages ---- */
.flash {
  padding: .8rem 1rem;
  border-radius: var(--radius-sm);
  margin-bottom: 1rem;
  font-size: .9rem;
  border: 1px solid transparent;
}
.flash-success { background: rgba(85, 209, 135, .1); border-color: rgba(85,209,135,.3); color: #b8f0cb; }
.flash-error   { background: rgba(255, 107, 107, .1); border-color: rgba(255,107,107,.3); color: #ffc4c4; }
.flash-warn    { background: rgba(255, 184, 77, .1);  border-color: rgba(255,184,77,.3);  color: #ffe0b0; }

/* ---- Badges ---- */
.badge {
  display: inline-flex;
  align-items: center;
  gap: .35rem;
  padding: .2rem .55rem;
  font-size: .72rem;
  font-weight: 650;
  letter-spacing: .03em;
  text-transform: uppercase;
  border-radius: 999px;
  background: rgba(255,255,255,.06);
  color: var(--fg-dim);
  border: 1px solid var(--border);
}
.badge[data-tier="toddler"]  { color: var(--tier-toddler);  border-color: color-mix(in oklab, var(--tier-toddler), transparent 65%); }
.badge[data-tier="children"] { color: var(--tier-children); border-color: color-mix(in oklab, var(--tier-children), transparent 65%); }
.badge[data-tier="eli5"]     { color: var(--tier-eli5);     border-color: color-mix(in oklab, var(--tier-eli5), transparent 65%); }
.badge[data-tier="teens"]    { color: var(--tier-teens);    border-color: color-mix(in oklab, var(--tier-teens), transparent 65%); }
.badge[data-tier="adults"]   { color: var(--tier-adults);   border-color: color-mix(in oklab, var(--tier-adults), transparent 65%); }

.badge-status-draft     { color: var(--warn); }
.badge-status-published { color: var(--ok); }
.badge-status-archived  { color: var(--muted); }

/* ---- Login ---- */
.auth-shell {
  min-height: calc(100vh - 120px);
  display: grid;
  place-items: center;
  padding: 2rem 1rem;
}
.auth-card {
  width: 100%;
  max-width: 380px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 2rem;
  box-shadow: var(--shadow);
}
.auth-card h1 { margin-bottom: 1.5rem; font-size: 1.5rem; }
.auth-card .btn { width: 100%; }

/* ---- Concept grid (home) ---- */
.hero {
  padding: 2rem 0 1.5rem;
  border-bottom: 1px solid var(--border);
  margin-bottom: 2rem;
}
.hero p {
  max-width: 60ch;
  font-size: 1.05rem;
  color: var(--fg-dim);
}

.tier-section { margin: 2.5rem 0; }
.tier-heading {
  display: flex;
  align-items: baseline;
  gap: .75rem;
  margin-bottom: 1rem;
}
.tier-heading .label {
  font-size: 1.1rem;
  font-weight: 650;
}
.tier-heading .sublabel {
  font-size: .85rem;
  color: var(--muted);
}
.tier-heading .count {
  margin-left: auto;
  font-size: .8rem;
  color: var(--muted);
}

.concept-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 1rem;
}

.concept-card {
  display: flex;
  flex-direction: column;
  gap: .65rem;
  padding: 1.15rem 1.15rem 1.25rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  text-decoration: none;
  color: var(--fg);
  transition: transform .15s ease, border-color .15s, box-shadow .2s;
  position: relative;
  overflow: hidden;
}
.concept-card::before {
  content: "";
  position: absolute;
  inset: 0 0 auto 0;
  height: 2px;
  background: var(--tier, var(--flow));
  opacity: .6;
}
.concept-card:hover {
  transform: translateY(-2px);
  border-color: var(--border-2);
  box-shadow: var(--shadow-sm);
  color: var(--fg);
}
.concept-card h3 {
  font-size: 1.02rem;
  line-height: 1.3;
  margin: 0;
}
.concept-card p {
  font-size: .85rem;
  margin: 0;
  color: var(--muted);
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.concept-card .meta {
  display: flex;
  align-items: center;
  gap: .5rem;
  font-size: .75rem;
  color: var(--muted);
  margin-top: auto;
}

.empty-state {
  padding: 3rem 1.5rem;
  text-align: center;
  border: 1px dashed var(--border-2);
  border-radius: var(--radius);
  color: var(--muted);
}
.empty-state h3 { color: var(--fg); margin-bottom: .25rem; }

/* ---- Utility ---- */
.row { display: flex; gap: .75rem; align-items: center; }
.row-between { justify-content: space-between; }
.stack > * + * { margin-top: 1rem; }
.muted { color: var(--muted); }
.small { font-size: .85rem; }