:root {
    --primary: #3A4650;          /* Your base color */
    --primary-dark: #2F3942;
    --primary-light: #E6E9EC;
    --primary-muted: #F2F4F6;
    --space-unit: 8px;
    --text-dark: #111111;
    --text-light: #FFFFFF;
    --text-muted: #6B6F74;

    --border: rgba(0,0,0,0.08);
}


:root {
    --font-primary: "helvetica-lt-pro", sans-serif;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: var(--font-primary);
    font-weight: 300; /* Light */
    font-style: normal;
    letter-spacing: 0.2px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

html {
    scroll-behavior: smooth;
}

.container {
    max-width: 860px;
    margin: 0 auto;
    padding: 5rem 1.5rem;
}

/* SECTION COLORS */

.section-title {
    font-weight: 400;
    font-size: clamp(32px, 4vw, 56px);
    letter-spacing: 1px;
    line-height: 1.1;
}
.section-light {
    background: #FFFFFF;
}

.section-muted {
    background: var(--primary-light);
}

.section-dark {
    background: var(--primary);
    color: var(--text-light);
}

.section-dark-alt {
    background: var(--primary-dark);
    color: var(--text-light);
}

/* TYPOGRAPHY */

h1, h2 {
    font-weight: 400; /* Roman */
}

strong {
    font-weight: 700; /* Bold */
}

em {
    font-style: italic;
}

.subtitle {
    color: rgba(255,255,255,0.75);
    max-width: 600px;
}

.subtitle-light {
    color: rgba(255,255,255,0.75);
    margin-bottom: 2rem;
}

p {
    margin-bottom: 1.5rem;
}

.list {
    list-style: none;
}

.list li {
    margin-bottom: 0.8rem;
    color: var(--text-muted);
}

/* AXIOMS */

.axioms p {
    border-left: 2px solid var(--primary);
    padding-left: 1rem;
    margin-bottom: calc(var(--space-unit) * 3.5);
}

.axiom-block {
    margin-bottom: 36px;
}

.axiom-block h4 {
    margin-bottom: 12px;
}

.axiom-block .layers p {
    border-left: none;
    padding-left: 0; /* remove inherited spacing */
}

/* BUTTONS */

.button {
    display: inline-block;
    padding: 0.7rem 1.4rem;
    font-size: 0.9rem;
    text-decoration: none;
    transition: all 0.25s ease;
    margin-top: 1rem;
}

.button.light {
    background: #FFFFFF;
    color: var(--primary);
}

.button.light:hover {
    background: var(--primary-light);
}

.button.outline {
    border: 1px solid var(--primary);
    color: var(--primary);
}

.button.outline:hover {
    background: var(--primary);
    color: #FFFFFF;
}

/* CTA alignment */

.cta {
    margin-top: 2rem;
}

.cta .button {
    margin-right: 1rem;
}

/* FOOTER */

footer {
    text-align: center;
    padding: 3rem 1rem;
    font-size: 0.85rem;
    color: var(--text-muted);
    background: #FFFFFF;
}

/* SUBTLE FADE-IN ANIMATION */

section {
    opacity: 0;
    transform: translateY(12px);
    animation: fadeIn 0.8s ease forwards;
    scroll-margin-top: 100px; /* adjust to navbar height */

}

section:nth-of-type(1) { animation-delay: 0.05s; }
section:nth-of-type(2) { animation-delay: 0.1s; }
section:nth-of-type(3) { animation-delay: 0.15s; }
section:nth-of-type(4) { animation-delay: 0.2s; }
section:nth-of-type(5) { animation-delay: 0.25s; }

@keyframes fadeIn {
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* AXIOMS SECTION CLEANUP */

#axioms {
    padding: 80px 0;
}

#axioms h2 {
    font-weight: 400;
    font-size: 40pt;
    margin: 0 0 40px 0; /* controlled spacing */
}

#axioms ul {
    list-style: none;
    padding: 0;
    margin: 0;
}

#axioms li {
    position: relative;
    padding-left: 24px;
    margin-bottom: 28px; /* consistent rhythm */
    font-weight: 300;
    line-height: 1.6;
}

/* left structural bar */
#axioms li::before {
    content: "";
    position: absolute;
    left: 0;
    top: 6px;
    width: 4px;
    height: 18px;
    background: #3f4a52; /* your blue-grey */
}


/* NAVBAR */

.navbar {
    background: #ffffff;
    border-bottom: 1px solid var(--border);
    position: sticky;
    top: 0;
    z-index: 100;
    transition: background 0.3s ease;
}

.nav-container {
    max-width: 860px;
    margin: 0 auto;
    padding: 1rem 1.5rem;
    display: flex;
    gap: 2rem;
    font-size: 0.9rem;
}

.navbar a {
    text-decoration: none;
    color: var(--primary);
    position: relative;
    padding-bottom: 4px;
    transition: color 0.2s ease;
}

.navbar a::after {
    content: "";
    position: absolute;
    left: 0;
    bottom: 0;
    width: 0%;
    height: 1px;
    background: var(--primary);
    transition: width 0.25s ease;
}

.navbar a:hover::after {
    width: 100%;
}

.navbar a.active {
    font-weight: 500;
}

/* VIEWPORT */

.viewport {
    position: relative;
    min-height: 60vh;
}

/* PANELS */

.panel {
    opacity: 0;
    visibility: hidden;
    position: absolute;
    width: 100%;
    transition: opacity 0.3s ease;
    animation: fadePanel 0.35s ease;    
}

.panel.active {
    opacity: 1;
    visibility: visible;
    position: relative;
}

@keyframes fadePanel {
    from {
        opacity: 0;
        transform: translateY(8px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* NAVBAR ARROW */

.navbar a {
    cursor: pointer;
    position: relative;
}

.navbar a.active::before {
    content: "→ ";
    position: absolute;
    left: -18px;
    color: var(--primary);
    font-weight: 500;
}

.suggested-questions {
    margin-top: 2.5rem;
    display: flex;
    flex-direction: column;
    gap: 1.25rem;
}

.suggested-questions p {
    font-style: italic;
    opacity: 0.75;
    transition: opacity 0.4s ease;
}

.suggested-questions p:hover {
    opacity: 1;
}

#explore h2 {
    margin-bottom: 1rem;
}

#explore p {
    line-height: 1.6;
}

.suggested-questions {
    margin-top: 3rem;
}

#hero {
    position: relative;
    height: 20vh;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    color: white;
    background: url("creased-paper.jpg") center center / cover no-repeat;
}

#hero::after {
    content: "";
    position: absolute;
    inset: 0;
    background: rgba(20, 30, 40, 0.65);
}

.hero-content {
    position: relative;
    z-index: 2;
}

.fold-illustration {
    margin: 3rem 0;
    text-align: center;
}

.fold-illustration img {
    max-width: 700px;
    width: 100%;
    height: auto;
    filter: grayscale(100%);
}

#explains .fold-compare {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 3rem;
}

.list {
    list-style: none;
    padding: 0;
    margin-top: 2rem;
}

.list li {
    margin-bottom: 0.9rem;
    opacity: 0.75;
    font-weight: 400;
}


.fold-compare {
    margin: 6rem auto 2rem auto;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 3rem;
    align-items: start;
}

.topology {
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
}

.topology img {
    width: 100%;
    height: auto;
    filter: grayscale(100%) contrast(98%) brightness(102%);
}

}

.caption {
    margin-top: 1rem;
    font-size: 0.85rem;
    opacity: 0.6;
    text-align: center;
}