:root {
    color-scheme: dark;

    --background: #101318;
    --panel: #191e26;
    --input: #11161d;
    --border: #343b47;
    --text: #f3f5f7;
    --muted: #aeb6c2;
    --accent: #ffb454;
    --error: #ff8b8b;
}

* {
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    min-height: 100vh;
    margin: 0;

    background: var(--background);
    color: var(--text);
    font-family: "Segoe UI", Arial, sans-serif;
    line-height: 1.5;
}

button,
input {
    font: inherit;
}

/* Shared header */

.site-header {
    position: sticky;
    top: 0;
    z-index: 1000;

    background: rgba(16, 19, 24, 0.96);
    border-bottom: 1px solid var(--border);
    backdrop-filter: blur(10px);
}

.site-nav {
    width: min(1100px, calc(100% - 32px));
    min-height: 64px;
    margin: 0 auto;

    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 24px;
}

.site-brand {
    display: inline-flex;
    align-items: center;
    gap: 10px;

    color: var(--text);
    font-size: 1.15rem;
    font-weight: 700;
    text-decoration: none;
    white-space: nowrap;
}

.site-brand:hover,
.site-brand:focus-visible {
    color: var(--accent);
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 24px;
}

.nav-links a {
    color: var(--muted);
    font-weight: 600;
    text-decoration: none;
}

.nav-links a:hover,
.nav-links a:focus-visible,
.nav-links a[aria-current="page"] {
    color: var(--accent);
}

.menu-toggle {
    display: none;
    width: 44px;
    height: 44px;
    padding: 10px;

    background: transparent;
    border: 1px solid var(--border);
    border-radius: 8px;
    cursor: pointer;
}

.menu-toggle span {
    display: block;
    width: 100%;
    height: 2px;
    margin: 5px 0;

    background: var(--text);
    border-radius: 2px;
    transition:
        transform 0.2s ease,
        opacity 0.2s ease;
}

.menu-toggle[aria-expanded="true"] span:nth-child(1) {
    transform: translateY(7px) rotate(45deg);
}

.menu-toggle[aria-expanded="true"] span:nth-child(2) {
    opacity: 0;
}

.menu-toggle[aria-expanded="true"] span:nth-child(3) {
    transform: translateY(-7px) rotate(-45deg);
}

/* Shared page layout */

.site-main {
    width: min(1100px, calc(100% - 32px));
    min-height: calc(100vh - 140px);
    margin: 0 auto;
    padding: 48px 0;
}

.content-narrow {
    width: min(720px, 100%);
    margin: 0 auto;
}

.page-heading {
    margin-bottom: 28px;
    text-align: center;
}

.page-heading h1 {
    margin: 0 0 8px;
    font-size: clamp(2rem, 6vw, 3rem);
}

.subtitle {
    color: var(--muted);
    font-size: 1.05rem;
}

.content-card {
    padding: 28px;

    background: var(--panel);
    border: 1px solid var(--border);
    border-radius: 14px;
    box-shadow: 0 12px 32px rgba(0, 0, 0, 0.22);
}

.content-card h2 {
    margin-top: 0;
}

.content-card p:last-child {
    margin-bottom: 0;
}

.site-footer {
    width: min(1100px, calc(100% - 32px));
    margin: 0 auto;
    padding: 0 0 28px;

    color: var(--muted);
    font-size: 0.85rem;
    text-align: center;
}

.content-card a {
    color: var(--accent);
}

.tool-listing h2 {
    margin-bottom: 6px;
}

.tool-listing p {
    margin-top: 0;
    color: var(--muted);
}

.tool-listing + .tool-listing {
    margin-top: 20px;
    padding-top: 20px;
    border-top: 1px solid var(--border);
}

/* Homepage */

.home-hero {
    width: min(820px, 100%);
    margin: 0 auto 48px;
    text-align: center;
}

.home-hero h1 {
    margin: 10px 0 18px;
    font-size: clamp(2.4rem, 7vw, 4rem);
    line-height: 1.08;
}

.eyebrow {
    margin: 0;

    color: var(--accent);
    font-size: 0.82rem;
    font-weight: 700;
    letter-spacing: 0.12em;
    text-transform: uppercase;
}

.home-hero-copy {
    max-width: 680px;
    margin: 0 auto;

    color: var(--muted);
    font-size: 1.12rem;
}

.home-actions {
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    gap: 12px;
    margin-top: 28px;
}

.button {
    display: inline-flex;
    min-height: 46px;
    padding: 11px 18px;

    align-items: center;
    justify-content: center;

    border: 1px solid var(--border);
    border-radius: 9px;

    font-weight: 700;
    text-decoration: none;
}

.button-primary {
    color: #101318;
    background: var(--accent);
    border-color: var(--accent);
}

.button-primary:hover,
.button-primary:focus-visible {
    filter: brightness(1.08);
}

.button-secondary {
    color: var(--text);
    background: var(--panel);
}

.button-secondary:hover,
.button-secondary:focus-visible {
    color: var(--accent);
    border-color: var(--accent);
}

.featured-tool {
    display: grid;
    grid-template-columns: 1.35fr 0.65fr;
    gap: 28px;
    padding: 32px;

    background: var(--panel);
    border: 1px solid var(--border);
    border-radius: 14px;
    box-shadow: 0 12px 32px rgba(0, 0, 0, 0.22);
}

.featured-tool h2 {
    margin: 8px 0 14px;
    font-size: 2rem;
}

.featured-tool-copy p:not(.eyebrow) {
    color: var(--muted);
}

.inline-link {
    color: var(--accent);
    font-weight: 700;
}

.featured-result {
    display: flex;
    min-height: 210px;
    padding: 24px;

    flex-direction: column;
    align-items: center;
    justify-content: center;

    text-align: center;
    background: var(--input);
    border: 1px solid var(--border);
    border-radius: 12px;
}

.featured-result span,
.featured-result small {
    color: var(--muted);
}

.featured-result strong {
    margin: 8px 0;

    color: var(--accent);
    font-size: 3rem;
    line-height: 1;
}

.home-section {
    margin-top: 48px;
}

.section-heading {
    margin-bottom: 20px;
}

.section-heading h2 {
    margin-bottom: 4px;
    font-size: 2rem;
}

.section-heading p {
    margin: 0;
    color: var(--muted);
}

.home-tool-grid {
    display: grid;
    grid-template-columns:
        repeat(auto-fit, minmax(250px, 1fr));
    gap: 16px;
}

.home-tool-card {
    display: block;
    padding: 24px;

    color: var(--text);
    text-decoration: none;
    background: var(--panel);
    border: 1px solid var(--border);
    border-radius: 12px;
}

.home-tool-card:hover,
.home-tool-card:focus-visible {
    border-color: var(--accent);
    transform: translateY(-2px);
}

.home-tool-card h3 {
    margin: 0 0 8px;
    color: var(--accent);
}

.home-tool-card p {
    margin: 0 0 14px;
    color: var(--muted);
}

.home-tool-card span {
    font-weight: 700;
}

/* Mobile navigation */

@media (max-width: 620px) {
    .home-actions {
        display: grid;
    }

    .button {
        width: 100%;
    }

    .featured-tool {
        grid-template-columns: 1fr;
        padding: 20px;
    }

    .featured-result {
        min-height: 170px;
    }

    .home-section {
        margin-top: 36px;
    }
    
    .site-nav {
        position: relative;
    }

    .menu-toggle {
        display: block;
    }

    .nav-links {
        display: none;
        position: absolute;
        top: calc(100% + 8px);
        left: 0;
        right: 0;

        padding: 12px;

        background: var(--panel);
        border: 1px solid var(--border);
        border-radius: 10px;
        box-shadow: 0 14px 30px rgba(0, 0, 0, 0.35);
    }

    .nav-links.is-open {
        display: grid;
        gap: 4px;
    }

    .nav-links a {
        padding: 12px;
        border-radius: 7px;
    }

    .nav-links a:hover,
    .nav-links a:focus-visible,
    .nav-links a[aria-current="page"] {
        background: var(--input);
    }

    .site-main {
        padding: 28px 0;
    }

    .content-card {
        padding: 20px;
    }
}

/* Compound Interest Calculator */

.compound-card {
    padding: 28px;

    background: var(--panel);
    border: 1px solid var(--border);
    border-radius: 14px;
    box-shadow: 0 12px 32px rgba(0, 0, 0, 0.22);
}

.compound-input-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 18px;
}

.compound-field {
    display: grid;
    gap: 8px;
}

.compound-field label {
    font-weight: 700;
}

.compound-field input {
    width: 100%;
    min-height: 52px;
    padding: 12px 16px;

    color: var(--text);
    background: var(--input);
    border: 1px solid var(--border);
    border-radius: 9px;
}

.compound-field input:focus {
    border-color: var(--accent);
    outline: 2px solid transparent;
    box-shadow: 0 0 0 3px rgba(255, 180, 84, 0.18);
}

.compound-input-suffix {
    position: relative;
}

.compound-input-suffix input {
    padding-right: 48px;
}

.compound-input-suffix span {
    position: absolute;
    top: 50%;
    right: 16px;

    color: var(--muted);
    font-weight: 700;
    transform: translateY(-50%);
    pointer-events: none;
}

.compound-results {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 14px;
    margin-top: 28px;
}

.compound-result {
    display: grid;
    min-height: 140px;
    padding: 20px;

    place-content: center;
    gap: 8px;

    text-align: center;
    background: var(--input);
    border: 1px solid var(--border);
    border-radius: 12px;
}

.compound-result span {
    color: var(--muted);
}

.compound-result strong {
    color: var(--accent);
    font-size: clamp(1.7rem, 4vw, 2.35rem);
    line-height: 1.1;
}

.compound-explanation {
    margin-top: 28px;
    padding-top: 26px;

    border-top: 1px solid var(--border);
}

.compound-explanation h2 {
    margin-top: 0;
}

.compound-explanation p {
    color: var(--muted);
}

.compound-explanation p:last-child {
    margin-bottom: 0;
}

.compound-disclaimer {
    margin: 24px auto 0;

    color: var(--muted);
    font-size: 0.9rem;
    text-align: center;
}

@media (max-width: 760px) {
    .compound-card {
        padding: 20px;
    }

    .compound-input-grid,
    .compound-results {
        grid-template-columns: 1fr;
    }

    .compound-result {
        min-height: 120px;
    }
}

/* Rule of 72 Calculator */

.rule72-card {
    padding: 28px;

    background: var(--panel);
    border: 1px solid var(--border);
    border-radius: 14px;
    box-shadow: 0 12px 32px rgba(0, 0, 0, 0.22);
}

.rule72-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 18px;
}

.rule72-panel {
    padding: 22px;

    background: var(--input);
    border: 1px solid var(--border);
    border-radius: 12px;
}

.rule72-panel h2 {
    margin: 0 0 6px;
    font-size: 1.35rem;
}

.rule72-panel-copy {
    margin: 0 0 20px;
    color: var(--muted);
}

.rule72-field {
    display: grid;
    gap: 8px;
}

.rule72-field label {
    font-weight: 700;
}

.rule72-input-suffix {
    position: relative;
}

.rule72-input-suffix input {
    width: 100%;
    min-height: 52px;
    padding: 12px 72px 12px 16px;

    color: var(--text);
    background: var(--background);
    border: 1px solid var(--border);
    border-radius: 9px;
}

.rule72-input-suffix input:focus {
    border-color: var(--accent);
    outline: 2px solid transparent;
    box-shadow: 0 0 0 3px rgba(255, 180, 84, 0.18);
}

.rule72-input-suffix span {
    position: absolute;
    top: 50%;
    right: 16px;

    color: var(--muted);
    font-weight: 700;
    transform: translateY(-50%);
    pointer-events: none;
}

.rule72-result {
    display: grid;
    min-height: 150px;
    margin-top: 22px;
    padding: 20px;

    place-content: center;
    gap: 8px;

    text-align: center;
    background: var(--background);
    border: 1px solid var(--border);
    border-radius: 10px;
}

.rule72-result span,
.rule72-result small {
    color: var(--muted);
}

.rule72-result strong {
    color: var(--accent);
    font-size: clamp(1.65rem, 4vw, 2.25rem);
    line-height: 1.15;
}

.rule72-explanation {
    margin-top: 28px;
    padding-top: 26px;

    border-top: 1px solid var(--border);
}

.rule72-explanation h2 {
    margin-top: 0;
}

.rule72-explanation p {
    color: var(--muted);
}

.rule72-formulas {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 14px;
    margin: 22px 0;
}

.rule72-formula {
    display: grid;
    gap: 8px;
    padding: 18px;

    background: var(--input);
    border: 1px solid var(--border);
    border-radius: 10px;
}

.rule72-formula span {
    color: var(--muted);
}

.rule72-formula code {
    color: var(--accent);
    font-size: 0.95rem;
}

.rule72-disclaimer {
    margin: 24px auto 0;

    color: var(--muted);
    font-size: 0.9rem;
    text-align: center;
}

@media (max-width: 760px) {
    .rule72-card {
        padding: 20px;
    }

    .rule72-grid,
    .rule72-formulas {
        grid-template-columns: 1fr;
    }

    .rule72-panel {
        padding: 18px;
    }

    .rule72-result {
        min-height: 125px;
    }
}