/* ========================================
   CSS Variables (Design Tokens)
   ======================================== */

:root {
    /* Colors - Primary */
    --color-primary-main: #2563EB;
    --color-primary-dark: #1D4ED8;
    --color-primary-light: #3B82F6;
    
    /* Colors - Secondary */
    --color-secondary-main: #10B981;
    --color-secondary-dark: #059669;
    --color-secondary-light: #34D399;
    
    /* Colors - Neutral */
    --color-neutral-900: #1F2937;
    --color-neutral-700: #374151;
    --color-neutral-500: #6B7280;
    --color-neutral-300: #D1D5DB;
    --color-neutral-100: #F3F4F6;
    --color-neutral-50: #F9FAFB;
    
    /* Colors - Status */
    --color-error: #EF4444;
    --color-warning: #F59E0B;
    --color-success: #10B981;
    --color-info: #3B82F6;
    
    /* Colors - Text */
    --color-text-primary: #1F2937;
    --color-text-secondary: #6B7280;
    --color-bg-primary: #FFFFFF;
    --color-bg-secondary: #F9FAFB;
    
    /* Typography - Headings */
    --font-heading1-size: 48px;
    --font-heading1-weight: 700;
    --font-heading1-lh: 1.2;
    
    --font-heading2-size: 36px;
    --font-heading2-weight: 700;
    --font-heading2-lh: 1.3;
    
    --font-heading3-size: 24px;
    --font-heading3-weight: 600;
    --font-heading3-lh: 1.4;
    
    /* Typography - Body */
    --font-body-large-size: 18px;
    --font-body-large-weight: 400;
    --font-body-large-lh: 1.6;
    
    --font-body-size: 16px;
    --font-body-weight: 400;
    --font-body-lh: 1.5;
    
    --font-caption-size: 14px;
    --font-caption-weight: 400;
    --font-caption-lh: 1.4;
    
    /* Spacing - Base Unit 4px */
    --spacing-xs: 4px;
    --spacing-sm: 8px;
    --spacing-md: 12px;
    --spacing-base: 16px;
    --spacing-lg: 24px;
    --spacing-xl: 32px;
    --spacing-2xl: 48px;
    --spacing-3xl: 64px;
    --spacing-4xl: 80px;
    --spacing-5xl: 96px;
    
    /* Border Radius */
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 16px;
    --radius-full: 9999px;
    
    /* Shadows */
    --shadow-light: 0 2px 8px rgba(0, 0, 0, 0.08);
    --shadow-medium: 0 4px 12px rgba(0, 0, 0, 0.12);
    --shadow-heavy: 0 8px 24px rgba(0, 0, 0, 0.16);
    
    /* Transitions */
    --transition-fast: 150ms ease-in-out;
    --transition-base: 250ms ease-in-out;
    --transition-slow: 350ms ease-in-out;
    
    /* Font Family */
    --font-family-primary: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
}

/* ========================================
   Global Styles
   ======================================== */

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-family-primary);
    font-size: var(--font-body-size);
    font-weight: var(--font-body-weight);
    line-height: var(--font-body-lh);
    color: var(--color-text-primary);
    background-color: var(--color-bg-primary);
}

/* ========================================
   Typography
   ======================================== */

h1, .h1 {
    font-size: var(--font-heading1-size);
    font-weight: var(--font-heading1-weight);
    line-height: var(--font-heading1-lh);
    margin-bottom: var(--spacing-lg);
}

h2, .h2 {
    font-size: var(--font-heading2-size);
    font-weight: var(--font-heading2-weight);
    line-height: var(--font-heading2-lh);
    margin-bottom: var(--spacing-lg);
}

h3, .h3 {
    font-size: var(--font-heading3-size);
    font-weight: var(--font-heading3-weight);
    line-height: var(--font-heading3-lh);
    margin-bottom: var(--spacing-md);
}

p {
    margin-bottom: var(--spacing-base);
}

a {
    color: var(--color-primary-main);
    text-decoration: none;
    transition: color var(--transition-fast);
}

a:hover {
    color: var(--color-primary-dark);
    text-decoration: underline;
}

ul, ol {
    margin-bottom: var(--spacing-base);
}

/* ========================================
   Container & Layout
   ======================================== */

.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-lg);
}

/* Sections */
section {
    padding: var(--spacing-4xl) 0;
}

section:nth-child(even) {
    background-color: var(--color-bg-secondary);
}

.section__title {
    font-size: var(--font-heading2-size);
    font-weight: var(--font-heading2-weight);
    text-align: center;
    margin-bottom: var(--spacing-3xl);
    color: var(--color-text-primary);
}

/* ========================================
   Buttons
   ======================================== */

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-md) var(--spacing-lg);
    font-family: var(--font-family-primary);
    font-size: var(--font-body-size);
    font-weight: 600;
    border: none;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all var(--transition-fast);
    text-decoration: none;
    white-space: nowrap;
}

/* Button Sizes */
.btn--large {
    padding: var(--spacing-base) var(--spacing-2xl);
    font-size: var(--font-body-large-size);
}

.btn--block {
    width: 100%;
}

/* Button Primary */
.btn--primary {
    background-color: var(--color-primary-main);
    color: white;
}

.btn--primary:hover:not(:disabled) {
    background-color: var(--color-primary-dark);
    transform: scale(1.02);
    box-shadow: var(--shadow-medium);
}

.btn--primary:focus {
    outline: 2px solid var(--color-primary-main);
    outline-offset: 2px;
}

.btn--primary:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

/* Button Secondary */
.btn--secondary {
    background-color: transparent;
    color: var(--color-primary-main);
    border: 2px solid var(--color-primary-main);
}

.btn--secondary:hover:not(:disabled) {
    background-color: var(--color-primary-main);
    color: white;
    transform: scale(1.02);
}

.btn--secondary:focus {
    outline: 2px solid var(--color-primary-main);
    outline-offset: 2px;
}

.btn--secondary:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

/* Button Tertiary */
.btn--tertiary {
    background-color: transparent;
    color: var(--color-primary-main);
    border: none;
}

.btn--tertiary:hover {
    text-decoration: underline;
}

/* ========================================
   Header & Navigation
   ======================================== */

.header_main {
    background-color: var(--color-bg-primary);
    border-bottom: 1px solid var(--color-neutral-100);
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: var(--shadow-light);
}

.header__wrapper {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-base) 0;
    gap: var(--spacing-2xl);
}

.header__logo {
    flex-shrink: 0;
}

.logo_bmitech {
    width: 120px;
    height: 40px;
    display: block;
}

.header__nav {
    flex: 1;
    display: flex;
    justify-content: center;
}

.nav__list {
    display: flex;
    list-style: none;
    gap: var(--spacing-2xl);
}

.nav__link {
    font-size: var(--font-body-size);
    font-weight: 500;
    color: var(--color-text-primary);
    position: relative;
    padding-bottom: var(--spacing-xs);
}

.nav__link::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background-color: var(--color-primary-main);
    transition: width var(--transition-fast);
}

.nav__link:hover::after {
    width: 100%;
}

.nav__link:focus {
    outline: 2px solid var(--color-primary-main);
    outline-offset: 4px;
    border-radius: var(--radius-sm);
}

/* ========================================
   Hero Section
   ======================================== */

.section_hero {
    padding: var(--spacing-5xl) 0;
    background: linear-gradient(135deg, #F9FAFB 0%, #F3F4F6 100%);
}

.section_hero .container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-3xl);
    align-items: center;
}

.hero__content {
    display: flex;
    flex-direction: column;
}

.hero__title {
    font-size: var(--font-heading1-size);
    font-weight: var(--font-heading1-weight);
    line-height: var(--font-heading1-lh);
    color: var(--color-text-primary);
    margin-bottom: var(--spacing-lg);
}

.hero__subtitle {
    font-size: var(--font-body-large-size);
    font-weight: var(--font-body-large-weight);
    line-height: var(--font-body-large-lh);
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-2xl);
}

.hero__buttons {
    display: flex;
    gap: var(--spacing-base);
    flex-wrap: wrap;
}

.hero__image {
    display: flex;
    align-items: center;
    justify-content: center;
}

.illustration_hero {
    width: 100%;
    height: auto;
    max-width: 400px;
}

/* ========================================
   About Section
   ======================================== */

.about__grid {
    display: grid;
    grid-template-columns: 1.2fr 1fr;
    gap: var(--spacing-3xl);
    align-items: start;
}

.about__text {
    font-size: var(--font-body-large-size);
    line-height: var(--font-body-large-lh);
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-lg);
}

.about__stats {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--spacing-lg);
}

.stat__card {
    background-color: var(--color-bg-primary);
    padding: var(--spacing-lg);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-light);
    border-left: 4px solid var(--color-primary-main);
    transition: all var(--transition-base);
}

.stat__card:hover {
    box-shadow: var(--shadow-medium);
    transform: translateY(-2px);
}

.stat__number {
    font-size: var(--font-heading2-size);
    font-weight: var(--font-heading2-weight);
    color: var(--color-primary-main);
    margin-bottom: var(--spacing-sm);
}

.stat__label {
    font-size: var(--font-body-size);
    color: var(--color-text-secondary);
}

/* ========================================
   Services Section
   ======================================== */

.services__grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-2xl);
}

.card__service {
    background-color: var(--color-bg-primary);
    padding: var(--spacing-2xl);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-light);
    transition: all var(--transition-base);
    border: 1px solid var(--color-neutral-100);
    display: flex;
    flex-direction: column;
}

.card__service:hover {
    box-shadow: var(--shadow-heavy);
    transform: translateY(-8px);
    border-color: var(--color-primary-main);
}

.card__header {
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: var(--spacing-lg);
    background-color: var(--color-bg-secondary);
    border-radius: var(--radius-md);
}

.card__title {
    font-size: var(--font-heading3-size);
    font-weight: var(--font-heading3-weight);
    margin-bottom: var(--spacing-md);
}

.card__description {
    font-size: var(--font-body-size);
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-lg);
    flex-grow: 1;
}

.card__link {
    font-weight: 600;
    color: var(--color-primary-main);
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-sm);
    transition: gap var(--transition-fast);
}

.card__link:hover {
    gap: var(--spacing-base);
}

/* ========================================
   NutriChat Section
   ======================================== */

.nutrichat__wrapper {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-3xl);
    align-items: center;
}

.nutrichat__subtitle {
    font-size: var(--font-heading3-size);
    font-weight: var(--font-heading3-weight);
    margin-bottom: var(--spacing-lg);
    color: var(--color-primary-main);
}

.nutrichat__text {
    font-size: var(--font-body-large-size);
    line-height: var(--font-body-large-lh);
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-2xl);
}

.nutrichat__features {
    list-style: none;
    display: grid;
    gap: var(--spacing-base);
}

.nutrichat__features li {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    font-size: var(--font-body-size);
}

.feature__icon {
    color: var(--color-secondary-main);
    font-weight: bold;
    font-size: 20px;
}

.nutrichat__image {
    display: flex;
    align-items: center;
    justify-content: center;
}

.illustration_ai {
    width: 100%;
    height: auto;
    max-width: 400px;
}

/* ========================================
   Advantages Section
   ======================================== */

.advantages__grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: var(--spacing-2xl);
}

.advantage__item {
    padding: var(--spacing-2xl);
    background-color: var(--color-bg-primary);
    border-radius: var(--radius-md);
    border: 1px solid var(--color-neutral-100);
    transition: all var(--transition-base);
}

.advantage__item:hover {
    box-shadow: var(--shadow-medium);
    transform: translateY(-4px);
}

.advantage__number {
    font-size: 48px;
    font-weight: 700;
    color: var(--color-primary-light);
    margin-bottom: var(--spacing-md);
    opacity: 0.6;
}

.advantage__title {
    font-size: var(--font-heading3-size);
    font-weight: var(--font-heading3-weight);
    margin-bottom: var(--spacing-md);
}

.advantage__description {
    font-size: var(--font-body-size);
    color: var(--color-text-secondary);
    line-height: var(--font-body-lh);
}

/* ========================================
   Tariffs Section
   ======================================== */

.tariffs__grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-2xl);
}

.card__tariff {
    background-color: var(--color-bg-primary);
    padding: var(--spacing-2xl);
    border-radius: var(--radius-md);
    border: 1px solid var(--color-neutral-100);
    transition: all var(--transition-base);
    display: flex;
    flex-direction: column;
    position: relative;
}

.card__tariff:hover {
    box-shadow: var(--shadow-heavy);
    transform: translateY(-8px);
}

.card__tariff--featured {
    border-color: var(--color-primary-main);
    box-shadow: var(--shadow-medium);
    transform: scale(1.02);
}

.tariff__badge {
    position: absolute;
    top: 0;
    right: var(--spacing-base);
    background-color: var(--color-primary-main);
    color: white;
    padding: var(--spacing-sm) var(--spacing-base);
    border-radius: 0 0 var(--radius-md) var(--radius-md);
    font-size: var(--font-caption-size);
    font-weight: 600;
}

.tariff__name {
    font-size: var(--font-heading3-size);
    font-weight: var(--font-heading3-weight);
    margin-bottom: var(--spacing-lg);
}

.tariff__price {
    display: flex;
    align-items: baseline;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-2xl);
}

.price__value {
    font-size: 48px;
    font-weight: 700;
    color: var(--color-primary-main);
}

.price__currency {
    font-size: var(--font-body-size);
    color: var(--color-text-secondary);
}

.price__period {
    font-size: var(--font-body-size);
    color: var(--color-text-secondary);
}

.tariff__features {
    list-style: none;
    margin-bottom: var(--spacing-2xl);
    flex-grow: 1;
}

.feature__item {
    padding: var(--spacing-sm) 0;
    font-size: var(--font-body-size);
    color: var(--color-text-secondary);
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
}

/* ========================================
   Contact Section
   ======================================== */

.contact__wrapper {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-3xl);
}

.contact__subtitle {
    font-size: var(--font-heading3-size);
    font-weight: var(--font-heading3-weight);
    margin-bottom: var(--spacing-2xl);
}

.contact__item {
    margin-bottom: var(--spacing-2xl);
}

.contact__item strong {
    display: block;
    color: var(--color-text-primary);
    margin-bottom: var(--spacing-sm);
    font-weight: 600;
}

.contact__item p {
    color: var(--color-text-secondary);
    margin-bottom: 0;
}

/* ========================================
   Forms
   ======================================== */

.form__group {
    margin-bottom: var(--spacing-lg);
    display: flex;
    flex-direction: column;
}

.form__label {
    font-size: var(--font-body-size);
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
    color: var(--color-text-primary);
}

.form__input,
.form__textarea {
    padding: var(--spacing-md) var(--spacing-base);
    font-family: var(--font-family-primary);
    font-size: var(--font-body-size);
    border: 1px solid var(--color-neutral-300);
    border-radius: var(--radius-sm);
    transition: all var(--transition-fast);
    background-color: var(--color-bg-primary);
    color: var(--color-text-primary);
}

.form__input:focus,
.form__textarea:focus {
    outline: none;
    border-color: var(--color-primary-main);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.form__input::placeholder,
.form__textarea::placeholder {
    color: var(--color-neutral-500);
}

.form__textarea {
    resize: vertical;
    font-family: var(--font-family-primary);
}

/* ========================================
   Footer
   ======================================== */

.footer_main {
    background-color: var(--color-neutral-900);
    color: white;
    padding: var(--spacing-4xl) 0 var(--spacing-2xl);
    margin-top: var(--spacing-5xl);
}

.footer__content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-2xl);
    margin-bottom: var(--spacing-3xl);
    padding-bottom: var(--spacing-2xl);
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.footer__column {
    display: flex;
    flex-direction: column;
}

.footer__title {
    font-size: var(--font-heading3-size);
    font-weight: var(--font-heading3-weight);
    margin-bottom: var(--spacing-lg);
}

.footer__text {
    color: rgba(255, 255, 255, 0.8);
    font-size: var(--font-body-size);
    line-height: var(--font-body-lh);
}

.footer__links {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.footer__links a {
    color: rgba(255, 255, 255, 0.8);
    text-decoration: none;
    transition: color var(--transition-fast);
    font-size: var(--font-body-size);
}

.footer__links a:hover {
    color: white;
}

.social__links {
    display: flex;
    gap: var(--spacing-lg);
    flex-wrap: wrap;
}

.social__link {
    color: rgba(255, 255, 255, 0.8);
    text-decoration: none;
    transition: color var(--transition-fast);
    font-size: var(--font-body-size);
}

.social__link:hover {
    color: var(--color-primary-light);
}

.footer__bottom {
    text-align: center;
}

.footer__copyright {
    font-size: var(--font-body-size);
    color: rgba(255, 255, 255, 0.6);
    margin-bottom: var(--spacing-sm);
}

.footer__compliance {
    font-size: var(--font-caption-size);
    color: rgba(255, 255, 255, 0.4);
    margin-bottom: 0;
}

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

/* Tablet (1024px) */
@media (max-width: 1024px) {
    .container {
        max-width: 960px;
    }

    section {
        padding: var(--spacing-3xl) 0;
    }

    .section_hero .container,
    .about__grid,
    .nutrichat__wrapper,
    .contact__wrapper {
        grid-template-columns: 1fr;
        gap: var(--spacing-2xl);
    }

    .header__nav {
        display: none;
    }

    .hero__title {
        font-size: 36px;
    }

    .services__grid,
    .tariffs__grid,
    .advantages__grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

/* Large Mobile (768px) */
@media (max-width: 768px) {
    .container {
        max-width: 100%;
        padding: 0 var(--spacing-base);
    }

    section {
        padding: var(--spacing-2xl) 0;
    }

    :root {
        --font-heading1-size: 36px;
        --font-heading2-size: 28px;
        --font-heading3-size: 20px;
        --font-body-large-size: 16px;
    }

    h1 {
        margin-bottom: var(--spacing-base);
    }

    .header__wrapper {
        padding: var(--spacing-md) 0;
    }

    .header__logo {
        flex-shrink: 0;
    }

    .header__logo svg {
        width: 100px;
        height: 33px;
    }

    .hero__buttons {
        flex-direction: column;
    }

    .btn--large {
        padding: var(--spacing-base) var(--spacing-lg);
    }

    .services__grid,
    .tariffs__grid,
    .advantages__grid {
        grid-template-columns: 1fr;
    }

    .about__stats {
        grid-template-columns: repeat(3, 1fr);
    }

    .footer__content {
        grid-template-columns: repeat(2, 1fr);
        gap: var(--spacing-lg);
    }
}

/* Mobile (375px) */
@media (max-width: 480px) {
    :root {
        --spacing-lg: 16px;
        --spacing-xl: 24px;
        --spacing-2xl: 32px;
        --spacing-3xl: 40px;
    }

    .container {
        padding: 0 var(--spacing-base);
    }

    section {
        padding: var(--spacing-xl) 0;
    }

    .header__wrapper {
        flex-wrap: wrap;
        gap: var(--spacing-md);
        padding: var(--spacing-md) 0;
    }

    .header__logo svg {
        width: 90px;
        height: 30px;
    }

    .btn {
        padding: var(--spacing-sm) var(--spacing-base);
        font-size: 14px;
    }

    .btn--large {
        padding: var(--spacing-base) var(--spacing-lg);
    }

    .section__title {
        font-size: 24px;
        margin-bottom: var(--spacing-xl);
    }

    .hero__title {
        font-size: 24px;
    }

    .hero__subtitle {
        font-size: 16px;
        margin-bottom: var(--spacing-lg);
    }

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

    .stat__card {
        padding: var(--spacing-base);
    }

    .tariff__price {
        margin-bottom: var(--spacing-lg);
    }

    .price__value {
        font-size: 32px;
    }

    .footer__content {
        grid-template-columns: 1fr;
        gap: var(--spacing-base);
    }

    .footer__title {
        font-size: 18px;
    }
}

/* ========================================
   Accessibility
   ======================================== */

@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
        scroll-behavior: auto !important;
    }
}

@media (prefers-color-scheme: dark) {
    :root {
        --color-text-primary: #F9FAFB;
        --color-text-secondary: #D1D5DB;
        --color-bg-primary: #1F2937;
        --color-bg-secondary: #111827;
    }
}

/* Focus Visible for accessibility */
*:focus-visible {
    outline: 2px solid var(--color-primary-main);
    outline-offset: 2px;
}

/* ========================================
   Loading & Performance
   ======================================== */

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

/* Lazy Loading */
img[loading="lazy"] {
    background-color: var(--color-neutral-100);
}

/* Print Styles */
@media print {
    .header_main,
    .footer_main,
    .btn {
        display: none;
    }

    section {
        page-break-inside: avoid;
        padding: var(--spacing-lg) 0;
    }

    a {
        text-decoration: underline;
    }
}