===== style.css =====

```css
/* =========================================================
   شرکت تسمه‌های صنعتی بینالود - Stylesheet
   Colors: Primary #FFD100 | Secondary #000000 | White | Light Gray
   ========================================================= */

/* ----- Reset & Base ----- */
*,
*::before,
*::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

:root {
    --color-primary: #FFD100;
    --color-secondary: #000000;
    --color-white: #FFFFFF;
    --color-light-gray: #F4F4F4;
    --color-gray: #6B6B6B;
    --color-border: #E0E0E0;
    --font-base: "Tahoma", "Vazirmatn", "Segoe UI", sans-serif;
    --max-width: 1200px;
    --radius: 8px;
    --transition: 0.25s ease;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-base);
    color: var(--color-secondary);
    background-color: var(--color-white);
    line-height: 1.8;
    direction: rtl;
    text-align: right;
}

img {
    max-width: 100%;
    height: auto;
    display: block;
}

a {
    text-decoration: none;
    color: inherit;
}

ul {
    list-style: none;
}

.container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 20px;
}

/* ----- Accessibility: Skip Link ----- */
.skip-link {
    position: absolute;
    top: -50px;
    right: 0;
    background: var(--color-primary);
    color: var(--color-secondary);
    padding: 10px 20px;
    z-index: 1000;
    transition: top var(--transition);
}

.skip-link:focus {
    top: 0;
}

/* ----- Buttons ----- */
.btn {
    display: inline-block;
    padding: 14px 32px;
    border-radius: var(--radius);
    font-weight: bold;
    font-size: 1rem;
    transition: transform var(--transition), box-shadow var(--transition), background-color var(--transition);
    border: 2px solid transparent;
}

.btn:hover,
.btn:focus-visible {
    transform: translateY(-2px);
}

.btn-primary {
    background-color: var(--color-primary);
    color: var(--color-secondary);
}

.btn-primary:hover,
.btn-primary:focus-visible {
    background-color: #E6BB00;
}

.btn-whatsapp {
    background-color: var(--color-secondary);
    color: var(--color-white);
    border-color: var(--color-secondary);
}

.btn-whatsapp:hover,
.btn-whatsapp:focus-visible {
    background-color: #222222;
}

/* ----- Header ----- */
.site-header {
    background-color: var(--color-white);
    border-bottom: 3px solid var(--color-primary);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding-top: 14px;
    padding-bottom: 14px;
}

.brand {
    display: flex;
    align-items: center;
    gap: 12px;
}

.logo {
    border-radius: 4px;
}

.brand-name {
    font-weight: bold;
    font-size: 1.1rem;
}

/* ----- Navigation ----- */
.main-nav {
    position: relative;
}

.nav-list {
    display: flex;
    gap: 28px;
}

.nav-list a {
    font-weight: 600;
    padding: 8px 4px;
    position: relative;
}

.nav-list a::after {
    content: "";
    position: absolute;
    bottom: -2px;
    right: 0;
    width: 0;
    height: 2px;
    background-color: var(--color-primary);
    transition: width var(--transition);
}

.nav-list a:hover::after,
.nav-list a:focus-visible::after {
    width: 100%;
}

.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
}

.nav-toggle-bar {
    width: 26px;
    height: 3px;
    background-color: var(--color-secondary);
    border-radius: 2px;
}

/* ----- Hero ----- */
.hero {
    background-color: var(--color-secondary);
    color: var(--color-white);
    padding: 90px 0;
    text-align: center;
    background-image: linear-gradient(180deg, #000000 0%, #1a1a1a 100%);
}

.hero-title {
    font-size: 2.2rem;
    font-weight: 800;
    line-height: 1.5;
    margin-bottom: 20px;
    color: var(--color-primary);
}

.hero-subtitle {
    font-size: 1.15rem;
    max-width: 700px;
    margin: 0 auto 36px;
    color: #E0E0E0;
}

.hero-buttons {
    display: flex;
    justify-content: center;
    gap: 18px;
    flex-wrap: wrap;
}

/* ----- Section Common ----- */
section {
    padding: 70px 0;
}

section h2 {
    font-size: 1.9rem;
    margin-bottom: 34px;
    text-align: center;
    position: relative;
}

section h2::after {
    content: "";
    display: block;
    width: 70px;
    height: 4px;
    background-color: var(--color-primary);
    margin: 14px auto 0;
    border-radius: 2px;
}

/* ----- About ----- */
.about {
    background-color: var(--color-light-gray);
}

.about p {
    max-width: 850px;
    margin: 0 auto 18px;
    font-size: 1.05rem;
    color: #333;
}

/* ----- Products ----- */
.products-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 30px;
}

.product-card {
    background-color: var(--color-white);
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    overflow: hidden;
    transition: box-shadow var(--transition), transform var(--transition);
}

.product-card:hover {
    box-shadow: 0 10px 24px rgba(0, 0, 0, 0.12);
    transform: translateY(-4px);
}

.product-card img {
    width: 100%;
    aspect-ratio: 4 / 3;
    object-fit: cover;
}

.product-card h3 {
    font-size: 1.2rem;
    padding: 18px 18px 8px;
    color: var(--color-secondary);
}

.product-card p {
    padding: 0 18px 20px;
    color: var(--color-gray);
    font-size: 0.98rem;
}

/* ----- Advantages ----- */
.advantages {
    background-color: var(--color-secondary);
    color: var(--color-white);
}

.advantages #advantages-heading {
    color: var(--color-white);
}

.advantages-list {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 24px;
}

.advantage-item {
    background-color: #141414;
    border: 1px solid #2a2a2a;
    border-radius: var(--radius);
    padding: 26px 18px;
    text-align: center;
    transition: transform var(--transition), border-color var(--transition);
}

.advantage-item:hover {
    transform: translateY(-4px);
    border-color: var(--color-primary);
}

.advantage-item h3 {
    color: var(--color-primary);
    font-size: 1.1rem;
    margin-bottom: 10px;
}

.advantage-item p {
    color: #cfcfcf;
    font-size: 0.95rem;
}

/* ----- Contact ----- */
.contact {
    background-color: var(--color-light-gray);
}

.contact-grid {
    display: flex;
    justify-content: center;
}

.contact-info {
    background-color: var(--color-white);
    border-radius: var(--radius);
    padding: 34px;
    max-width: 600px;
    width: 100%;
    border: 1px solid var(--color-border);
}

.contact-list li {
    display: flex;
    gap: 10px;
    padding: 12px 0;
    border-bottom: 1px solid var(--color-border);
    flex-wrap: wrap;
}

.contact-list li:last-child {
    border-bottom: none;
}

.contact-label {
    font-weight: bold;
    min-width: 90px;
}

.contact-list a {
    color: var(--color-secondary);
    font-weight: 600;
}

.contact-list a:hover {
    color: #8a7000;
}

.contact-buttons {
    display: flex;
    gap: 16px;
    margin-top: 26px;
    flex-wrap: wrap;
}

address {
    font-style: normal;
}

/* ----- Footer ----- */
.site-footer {
    background-color: var(--color-secondary);
    color: var(--color-white);
    padding: 40px 0 24px;
    text-align: center;
}

.footer-brand {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    margin-bottom: 14px;
    font-weight: bold;
}

.footer-logo {
    border-radius: 4px;
}

.footer-address,
.footer-contact {
    color: #cfcfcf;
    font-size: 0.95rem;
    margin-bottom: 8px;
}

.footer-contact a {
    color: var(--color-primary);
}

.footer-copy {
    margin-top: 18px;
    font-size: 0.85rem;
    color: #888;
}

/* =========================================================
   Responsive
   ========================================================= */

/* Tablet */
@media (max-width: 992px) {
    .products-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .advantages-list {
        grid-template-columns: repeat(2, 1fr);
    }

    .hero-title {
        font-size: 1.9rem;
    }
}

/* Mobile */
@media (max-width: 768px) {
    .nav-toggle {
        display: flex;
    }

    .nav-list {
        position: absolute;
        top: calc(100% + 14px);
        left: 0;
        right: 0;
        background-color: var(--color-white);
        flex-direction: column;
        gap: 0;
        border: 1px solid var(--color-border);
        border-radius: var(--radius);
        overflow: hidden;
        max-height: 0;
        transition: max-height var(--transition);
    }

    .nav-list.is-open {
        max-height: 400px;
    }

    .nav-list li {
        border-bottom: 1px solid var(--color-border);
    }

    .nav-list li:last-child {
        border-bottom: none;
    }

    .nav-list a {
        display: block;
        padding: 14px 18px;
    }

    .nav-list a::after {
        display: none;
    }

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

    .advantages-list {
        grid-template-columns: 1fr;
    }

    .hero {
        padding: 60px 0;
    }

    .hero-title {
        font-size: 1.6rem;
    }

    .hero-subtitle {
        font-size: 1rem;
    }

    section {
        padding: 50px 0;
    }

    section h2 {
        font-size: 1.5rem;
    }
}

/* Small Mobile */
@media (max-width: 480px) {
    .hero-buttons,
    .contact-buttons {
        flex-direction: column;
        align-items: stretch;
    }

    .btn {
        text-align: center;
    }

    .contact-info {
        padding: 24px 18px;
    }
}
```