/* 
  SRISUN - Premium Cleantech Design System
  Engineering-first. Minimal. Architecturally Elegant.
*/

:root {
    /* Colors - Clean & Trustworthy */
    --color-bg: #FFFFFF;
    --color-bg-alt: #FBFBFB;
    --color-black: #000000;
    --color-text-main: #1D1D1F;
    --color-text-sub: #6E6E73;
    --color-accent: #0071E3;
    /* Premium Tech Blue */
    --color-border: #D2D2D7;

    /* Typography */
    --font-stack: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;

    /* Spacing */
    --section-pad: 120px;
    --container-width: 1100px;

    /* Animation */
    --ease: cubic-bezier(0.25, 0.1, 0.25, 1);
    --transition: all 0.4s var(--ease);
}

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

body {
    font-family: var(--font-stack);
    background-color: var(--color-bg);
    color: var(--color-text-main);
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
    word-spacing: -0.01em;
}

.container {
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 0 40px;
}

/* ===== Navigation ===== */
.nav {
    position: fixed;
    top: 0;
    width: 100%;
    z-index: 1000;
    background: rgba(255, 255, 255, 0.8);
    backdrop-filter: saturate(180%) blur(20px);
    border-bottom: 1px solid rgba(0, 0, 0, 0.05);
}

.nav-inner {
    height: 64px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.brand-logo {
    display: flex;
    align-items: center;
    gap: 12px;
    text-decoration: none;
    color: var(--color-black);
    font-weight: 800;
    font-size: 1.2rem;
    letter-spacing: -0.03em;
}

.logo-img {
    height: 28px;
    width: auto;
    border-radius: 4px;
}

.nav-links {
    display: flex;
    list-style: none;
    gap: 32px;
}

.nav-links a {
    text-decoration: none;
    color: var(--color-text-main);
    font-size: 0.85rem;
    font-weight: 500;
    opacity: 0.8;
    transition: var(--transition);
}

.nav-links a:hover {
    opacity: 1;
}

.nav-cta {
    background: var(--color-black);
    color: white;
    padding: 8px 18px;
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 600;
    text-decoration: none;
    transition: var(--transition);
    border: none;
    cursor: pointer;
    display: inline-block;
    z-index: 1001;
}

.nav-cta:hover {
    background: #333;
}

/* ===== Hero Section ===== */
.hero {
    position: relative;
    height: 100vh;
    display: flex;
    align-items: center;
    background-color: #000;
    overflow: hidden;
}

.hero-bg {
    position: absolute;
    inset: 0;
    background-image: url('images/hero-original.png');
    background-size: cover;
    background-position: center;
    opacity: 0.6;
}

.hero-content {
    position: relative;
    z-index: 2;
    color: white;
    max-width: 800px;
}

.hero-tagline {
    font-size: 1rem;
    font-weight: 600;
    letter-spacing: 2px;
    text-transform: uppercase;
    margin-bottom: 24px;
    opacity: 0.9;
    display: block;
}

.hero-h1 {
    font-size: clamp(3.5rem, 8vw, 5.5rem);
    line-height: 1.05;
    font-weight: 800;
    letter-spacing: -0.04em;
    margin-bottom: 32px;
}

.hero-p {
    font-size: 1.4rem;
    font-weight: 400;
    line-height: 1.4;
    max-width: 600px;
    margin-bottom: 48px;
    opacity: 0.9;
}

.btn-primary {
    display: inline-block;
    background: white;
    color: black;
    padding: 16px 40px;
    border-radius: 30px;
    font-weight: 600;
    text-decoration: none;
    transition: var(--transition);
}

.btn-primary:hover {
    transform: scale(1.05);
    background: #f5f5f7;
}

/* ===== Content Sections ===== */
.section {
    padding: var(--section-pad) 0;
}

.section-alt {
    background: var(--color-bg-alt);
}

.section-header {
    margin-bottom: 80px;
    max-width: 700px;
}

.label {
    font-size: 0.9rem;
    font-weight: 700;
    color: var(--color-accent);
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-bottom: 16px;
    display: block;
}

.h2 {
    font-size: clamp(2rem, 4vw, 3rem);
    font-weight: 800;
    letter-spacing: -0.03em;
    line-height: 1.1;
    margin-bottom: 24px;
}

.copy-large {
    font-size: 1.4rem;
    color: var(--color-text-sub);
    line-height: 1.5;
}

/* ===== Grid Systems ===== */
.grid-2 {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 40px;
}

.grid-3 {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 32px;
}

.grid-4 {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 48px;
}

/* ===== Feature Cards ===== */
.benefit-card {
    border-top: 1px solid var(--color-border);
    padding-top: 32px;
}

.benefit-num {
    font-size: 0.8rem;
    font-weight: 800;
    color: var(--color-text-sub);
    margin-bottom: 16px;
    display: block;
}

.benefit-h {
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: 12px;
}

.benefit-p {
    font-size: 1rem;
    color: var(--color-text-sub);
}

/* ===== Solution Cards ===== */
.solution-card {
    background: white;
    border-radius: 20px;
    overflow: hidden;
    box-shadow: 0 4px 30px rgba(0, 0, 0, 0.02);
    border: 1px solid #efeff2;
    transition: var(--transition);
}

.solution-card:hover {
    transform: translateY(-8px);
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.06);
}

.solution-img {
    height: 350px;
    background-size: cover;
    background-position: center;
}

.solution-body {
    padding: 40px;
}

.solution-list {
    margin-top: 24px;
    list-style: none;
}

.solution-list li {
    padding-left: 20px;
    position: relative;
    margin-bottom: 12px;
    font-size: 0.95rem;
    color: var(--color-text-sub);
}

.solution-list li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 10px;
    width: 6px;
    height: 6px;
    background: var(--color-accent);
    border-radius: 50%;
}

/* ===== Estimator Tool ===== */
.estimator-card {
    background: white;
    padding: 60px;
    border-radius: 24px;
    border: 1px solid var(--color-border);
    max-width: 700px;
    margin: 0 auto;
}

.input-field {
    width: 100%;
    padding: 20px;
    border-radius: 12px;
    border: 1px solid var(--color-border);
    font-size: 1rem;
    margin-bottom: 24px;
    background: #f9f9f9;
    transition: var(--transition);
}

.input-field:focus {
    outline: none;
    border-color: var(--color-black);
    background: white;
}

.btn-submit {
    width: 100%;
    padding: 20px;
    background: var(--color-black);
    color: white;
    border: none;
    border-radius: 12px;
    font-weight: 700;
    font-size: 1rem;
    cursor: pointer;
    transition: var(--transition);
}

.btn-submit:hover {
    background: #222;
}

.result-card {
    margin-top: 48px;
    padding-top: 48px;
    border-top: 1px solid var(--color-border);
    display: none;
}

.result-val {
    font-size: 3rem;
    font-weight: 800;
    color: var(--color-accent);
}

/* ===== FAQ ===== */
.faq-grid {
    border-top: 1px solid var(--color-border);
}

.faq-item {
    border-bottom: 1px solid var(--color-border);
    padding: 32px 0;
}

.faq-q {
    font-size: 1.25rem;
    font-weight: 700;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: var(--transition);
}

.faq-q::after {
    content: '+';
    font-weight: 400;
    font-size: 1.5rem;
}

.faq-item[data-open="true"] .faq-q::after {
    content: '−';
}

.faq-a {
    max-height: 0;
    overflow: hidden;
    color: var(--color-text-sub);
    font-size: 1rem;
    line-height: 1.6;
    transition: max-height 0.4s var(--ease), padding 0.4s var(--ease);
}

.faq-item[data-open="true"] .faq-a {
    max-height: 200px;
    padding-top: 20px;
}

/* ===== Footer ===== */
.footer {
    background: #f5f5f7;
    padding: 100px 0 40px;
}

.footer-grid {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1fr;
    gap: 48px;
    margin-bottom: 80px;
}

.footer-brand {
    font-size: 1.5rem;
    font-weight: 800;
    margin-bottom: 24px;
}

.footer-links h4 {
    margin-bottom: 24px;
    font-size: 0.8rem;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.footer-links ul {
    list-style: none;
}

.footer-links li {
    margin-bottom: 12px;
}

.footer-links a {
    text-decoration: none;
    color: var(--color-text-sub);
    font-size: 0.9rem;
    transition: var(--transition);
}

.footer-links a:hover {
    color: var(--color-black);
}

.footer-bottom {
    text-align: center;
    padding-top: 40px;
    border-top: 1px solid var(--color-border);
    font-size: 0.8rem;
    color: var(--color-text-sub);
}

/* Responsive */
@media (max-width: 1024px) {

    .grid-4,
    .grid-3 {
        grid-template-columns: 1fr 1fr;
    }

    .grid-2 {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 768px) {
    .hero-h1 {
        font-size: 3rem;
    }

    .footer-grid {
        grid-template-columns: 1fr;
    }

    .grid-4,
    .grid-3 {
        grid-template-columns: 1fr;
    }

    .section-pad {
        --section-pad: 80px;
    }

    .nav-links {
        display: none;
    }
}