/* ============================================================
   Researchly — global stylesheet
   Fonts: Instrument Sans (variable 400–700) + Instrument Serif,
   self-hosted in ../fonts/.
   ============================================================ */

/* ---- Instrument Sans — italic ---- */
@font-face {
  font-family: 'Instrument Sans';
  font-style: italic;
  font-weight: 400 700;
  font-stretch: 100%;
  font-display: swap;
  src: url('../fonts/instrument-sans-italic-latin-ext.woff2') format('woff2');
  unicode-range: U+0100-02BA, U+02BD-02C5, U+02C7-02CC, U+02CE-02D7, U+02DD-02FF, U+0304, U+0308, U+0329, U+1D00-1DBF, U+1E00-1E9F, U+1EF2-1EFF, U+2020, U+20A0-20AB, U+20AD-20C0, U+2113, U+2C60-2C7F, U+A720-A7FF;
}
@font-face {
  font-family: 'Instrument Sans';
  font-style: italic;
  font-weight: 400 700;
  font-stretch: 100%;
  font-display: swap;
  src: url('../fonts/instrument-sans-italic-latin.woff2') format('woff2');
  unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
}

/* ---- Instrument Sans — normal (variable weight 400–700) ---- */
@font-face {
  font-family: 'Instrument Sans';
  font-style: normal;
  font-weight: 400 700;
  font-stretch: 100%;
  font-display: swap;
  src: url('../fonts/instrument-sans-latin-ext.woff2') format('woff2');
  unicode-range: U+0100-02BA, U+02BD-02C5, U+02C7-02CC, U+02CE-02D7, U+02DD-02FF, U+0304, U+0308, U+0329, U+1D00-1DBF, U+1E00-1E9F, U+1EF2-1EFF, U+2020, U+20A0-20AB, U+20AD-20C0, U+2113, U+2C60-2C7F, U+A720-A7FF;
}
@font-face {
  font-family: 'Instrument Sans';
  font-style: normal;
  font-weight: 400 700;
  font-stretch: 100%;
  font-display: swap;
  src: url('../fonts/instrument-sans-latin.woff2') format('woff2');
  unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
}

/* ---- Instrument Serif — italic ---- */
@font-face {
  font-family: 'Instrument Serif';
  font-style: italic;
  font-weight: 400;
  font-display: swap;
  src: url('../fonts/instrument-serif-italic-latin-ext.woff2') format('woff2');
  unicode-range: U+0100-02BA, U+02BD-02C5, U+02C7-02CC, U+02CE-02D7, U+02DD-02FF, U+0304, U+0308, U+0329, U+1D00-1DBF, U+1E00-1E9F, U+1EF2-1EFF, U+2020, U+20A0-20AB, U+20AD-20C0, U+2113, U+2C60-2C7F, U+A720-A7FF;
}
@font-face {
  font-family: 'Instrument Serif';
  font-style: italic;
  font-weight: 400;
  font-display: swap;
  src: url('../fonts/instrument-serif-italic-latin.woff2') format('woff2');
  unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
}

/* ---- Instrument Serif — normal ---- */
@font-face {
  font-family: 'Instrument Serif';
  font-style: normal;
  font-weight: 400;
  font-display: swap;
  src: url('../fonts/instrument-serif-latin-ext.woff2') format('woff2');
  unicode-range: U+0100-02BA, U+02BD-02C5, U+02C7-02CC, U+02CE-02D7, U+02DD-02FF, U+0304, U+0308, U+0329, U+1D00-1DBF, U+1E00-1E9F, U+1EF2-1EFF, U+2020, U+20A0-20AB, U+20AD-20C0, U+2113, U+2C60-2C7F, U+A720-A7FF;
}
@font-face {
  font-family: 'Instrument Serif';
  font-style: normal;
  font-weight: 400;
  font-display: swap;
  src: url('../fonts/instrument-serif-latin.woff2') format('woff2');
  unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
}

/* ---- Base ---- */
html, body {
  margin: 0;
  padding: 0;
  background: #fff;
}
body {
  font-family: 'Instrument Sans', sans-serif;
  color: oklch(0.21 0.01 262);
  -webkit-font-smoothing: antialiased;
}
a {
  color: oklch(0.21 0.01 262);
  text-decoration: none;
}
a:hover {
  color: oklch(0.4 0.015 262);
}

/* ---- Nav links ---- */
.nav-link {
  color: oklch(0.48 0.015 262);
}
.nav-link:hover {
  color: oklch(0.21 0.01 262);
}

/* ---- Buttons ---- */
.btn-dark {
  color: #fff;
  background: oklch(0.21 0.01 262);
}
.btn-dark:hover {
  color: #fff;
  background: #000;
}
.btn-light {
  color: oklch(0.25 0.01 262);
  background: #fff;
  border: 1px solid oklch(0.9 0.004 262);
}
.btn-light:hover {
  color: oklch(0.21 0.01 262);
  border-color: oklch(0.75 0.008 262);
}

/* ---- Feature cards ---- */
.feature-card {
  transition: border-color 0.2s;
}
.feature-card:hover {
  border-color: oklch(0.75 0.008 262);
}

/* ---- Methodology: interactive engine layers ---- */
.layer-cyl {
  cursor: pointer;
  opacity: 0.32;
  transition: opacity 0.25s, transform 0.25s;
}
.layer-cyl.active {
  opacity: 1;
  transform: translateX(10px);
}
.layer-row {
  cursor: pointer;
  border-left: 2px solid oklch(0.93 0.003 262);
  background: transparent;
  transition: background 0.2s;
}
.layer-row:hover {
  background: oklch(0.985 0.001 262);
}
.layer-row.active {
  border-left-color: oklch(0.21 0.01 262);
  background: oklch(0.985 0.001 262);
}