/* ============================================
   YUSIKO PORTFOLIO - PRODUCTION CSS
   AI Systems Engineer · Multi-Model Architect
   ============================================ */

/* CSS Variables & Design Tokens */
:root {
    /* Colors */
    --color-primary: #1C212B;
    --color-secondary: #677084;
    --color-accent: #C4FFA0;
    --color-accent-dark: #9EE376;
    --color-background: #ffffff;
    --color-surface: #f8f9fa;
    --color-border: rgba(28, 33, 43, 0.1);
    --color-border-hover: rgba(28, 33, 43, 0.2);
    --color-gradient-start: #9282F8;
    --color-gradient-end: #C4FFA0;
    --color-success: #10B981;
    --color-muted: #9CA3AF;

    /* Typography */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 2rem;
    --font-size-4xl: 2.5rem;

    /* Spacing */
    --spacing-1: 0.25rem;
    --spacing-2: 0.5rem;
    --spacing-3: 0.75rem;
    --spacing-4: 1rem;
    --spacing-5: 1.25rem;
    --spacing-6: 1.5rem;
    --spacing-8: 2rem;
    --spacing-10: 2.5rem;
    --spacing-12: 3rem;
    --spacing-16: 4rem;
    --spacing-20: 5rem;

    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.625rem;
    --radius-xl: 1rem;
    --radius-full: 9999px;

    /* Shadows */
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);

    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 300ms ease;
    --transition-slow: 500ms ease;

    /* Container */
    --container-max: 70.9rem;
}

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

html {
    scroll-behavior: smooth;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    line-height: 1.6;
    color: var(--color-secondary);
    background-color: var(--color-background);
}

/* Typography */
h1,
h2,
h3,
h4,
h5,
h6 {
    color: var(--color-primary);
    font-weight: 500;
    line-height: 1.3;
}

h1 {
    font-size: var(--font-size-3xl);
    font-weight: 400;
}

h2 {
    font-size: var(--font-size-2xl);
}

h3 {
    font-size: var(--font-size-xl);
}

h4 {
    font-size: var(--font-size-lg);
    font-weight: 500;
}

h5 {
    font-size: var(--font-size-base);
    font-weight: 500;
}

p {
    color: var(--color-secondary);
    font-weight: 400;
}

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

a:hover {
    color: var(--color-primary);
}

ul,
ol {
    list-style: none;
}

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

/* Container */
.container {
    width: 100%;
    max-width: var(--container-max);
    margin: 0 auto;
    padding: 0 var(--spacing-5);
}

@media (min-width: 640px) {
    .container {
        padding: 0 var(--spacing-6);
    }
}

/* Content Wrapper */
.content-wrapper {
    border-left: 1px solid var(--color-border);
    border-right: 1px solid var(--color-border);
}

.content-inner {
    max-width: 48rem;
    margin: 0 auto;
    padding: var(--spacing-10) var(--spacing-4);
}

@media (min-width: 640px) {
    .content-inner {
        padding: var(--spacing-16) var(--spacing-6);
    }
}

/* Divider */
.divider {
    height: 1px;
    background: linear-gradient(90deg,
            transparent,
            var(--color-border) 20%,
            var(--color-border) 80%,
            transparent);
    margin: 0 auto;
    max-width: var(--container-max);
}

/* Section Label */
.section-label {
    font-size: var(--font-size-sm);
    text-transform: uppercase;
    letter-spacing: 2px;
    font-weight: 500;
    color: var(--color-primary);
    margin-bottom: var(--spacing-4);
}

/* ============================================
   HEADER STYLES
   ============================================ */
header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 100;
    background: var(--color-primary);
    overflow: hidden;
}

.header-bg {
    position: absolute;
    inset: 0;
    opacity: 0.3;
    background: linear-gradient(135deg, var(--color-gradient-start), var(--color-gradient-end));
    background-size: 200% 200%;
    animation: gradientShift 8s ease infinite;
}

@keyframes gradientShift {

    0%,
    100% {
        background-position: 0% 50%;
    }

    50% {
        background-position: 100% 50%;
    }
}

.header-content {
    position: relative;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-3) var(--spacing-4);
    min-height: 0;
}

/* Spacer for fixed header */
.header-spacer {
    height: 0;
}

/* ============================================
   HERO SECTION
   ============================================ */
.hero-section {
    padding-top: var(--spacing-8);
}

.hero-banner {
    width: 100%;
    height: 18rem;
    overflow: hidden;
    background: linear-gradient(135deg,
            #0B0B0B 0%,
            #1a1a2e 25%,
            #16213e 50%,
            #0f3460 75%,
            #0B0B0B 100%);
    background-size: 400% 400%;
    animation: heroGradient 15s ease infinite;
    position: relative;
}

.hero-banner::before {
    content: '';
    position: absolute;
    inset: 0;
    background: radial-gradient(circle at 30% 50%, rgba(196, 255, 160, 0.15) 0%, transparent 50%),
        radial-gradient(circle at 70% 50%, rgba(146, 130, 248, 0.15) 0%, transparent 50%);
    animation: orbFloat 10s ease-in-out infinite;
}

@keyframes heroGradient {

    0%,
    100% {
        background-position: 0% 50%;
    }

    50% {
        background-position: 100% 50%;
    }
}

@keyframes orbFloat {

    0%,
    100% {
        transform: translateY(0);
    }

    50% {
        transform: translateY(-10px);
    }
}

.hero-profile {
    position: relative;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-3);
    padding: 5.5rem var(--spacing-4) var(--spacing-8);
}

@media (min-width: 500px) {
    .hero-profile {
        flex-direction: row;
        align-items: flex-start;
        justify-content: space-between;
        gap: var(--spacing-3);
        padding: 5.5rem var(--spacing-6) var(--spacing-12);
    }
}

.hero-avatar-wrapper {
    position: absolute;
    top: 0;
    transform: translateY(-50%);
}

.hero-avatar {
    width: 145px;
    height: 145px;
    border-radius: 50%;
    border: 4px solid white;
    background: linear-gradient(135deg, var(--color-accent), var(--color-gradient-start));
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 3rem;
    font-weight: 600;
    color: var(--color-primary);
    position: relative;
    box-shadow: var(--shadow-lg);
    overflow: hidden;
}

.hero-avatar-img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    border-radius: 50%;
}

.hero-avatar::after {
    content: '';
    position: absolute;
    bottom: 10px;
    right: 20px;
    width: 16px;
    height: 16px;
    background: var(--color-success);
    border: 2px solid white;
    border-radius: 50%;
}

.hero-info {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-2);
    text-align: center;
}

@media (min-width: 500px) {
    .hero-info {
        text-align: left;
        gap: var(--spacing-3);
    }
}

.hero-name {
    font-size: var(--font-size-2xl);
}

@media (min-width: 768px) {
    .hero-name {
        font-size: var(--font-size-3xl);
    }
}

.hero-title {
    color: var(--color-gradient-start);
    font-weight: 400;
}

.hero-location {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-2);
    color: var(--color-primary);
}

@media (min-width: 500px) {
    .hero-location {
        justify-content: flex-start;
    }
}

.hero-location svg {
    width: 20px;
    height: 20px;
    color: var(--color-secondary);
}

.hero-actions {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-4);
}

@media (min-width: 768px) {
    .hero-actions {
        flex-direction: row;
    }
}

.social-links {
    display: flex;
    align-items: center;
    gap: var(--spacing-2);
}

.social-link {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 44px;
    height: 44px;
    border: 1px solid var(--color-border);
    border-radius: 50%;
    transition: all var(--transition-fast);
}

.social-link:hover {
    background: rgba(28, 33, 43, 0.05);
    border-color: var(--color-border-hover);
    transform: translateY(-2px);
}

.social-link svg {
    width: 18px;
    height: 18px;
    color: var(--color-primary);
}

.btn-primary {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-3);
    padding: var(--spacing-3) var(--spacing-5);
    background: var(--color-primary);
    color: white;
    border-radius: var(--radius-full);
    font-weight: 600;
    font-size: var(--font-size-sm);
    transition: all var(--transition-fast);
    border: 2px solid transparent;
    background-image: linear-gradient(var(--color-primary), var(--color-primary)),
        linear-gradient(96.09deg, var(--color-gradient-start) 12.17%, var(--color-accent) 90.71%);
    background-origin: border-box;
    background-clip: padding-box, border-box;
}

.btn-primary:hover {
    background: linear-gradient(96.09deg, var(--color-gradient-start) 12.17%, var(--color-accent) 90.71%);
    color: var(--color-primary);
    transform: translateY(-2px);
}

.btn-primary svg {
    width: 14px;
    height: 14px;
}

@media (min-width: 640px) {
    .btn-primary {
        font-size: var(--font-size-base);
    }
}

/* Hero Tagline */
.hero-tagline {
    padding: var(--spacing-8) var(--spacing-4);
    text-align: center;
    border-top: 1px solid var(--color-border);
}

@media (min-width: 640px) {
    .hero-tagline {
        padding: var(--spacing-10) var(--spacing-6);
    }
}

.hero-tagline p {
    max-width: 42rem;
    margin: 0 auto;
    font-size: var(--font-size-lg);
    line-height: 1.7;
}

/* ============================================
   ABOUT SECTION
   ============================================ */
.about-section {
    background: url('data:image/svg+xml,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100"><defs><pattern id="grain" patternUnits="userSpaceOnUse" width="100" height="100"><circle cx="50" cy="50" r="0.5" fill="rgba(28,33,43,0.03)"/></pattern></defs><rect width="100" height="100" fill="url(%23grain)"/></svg>');
}

.about-content {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-8);
}

@media (min-width: 640px) {
    .about-content {
        gap: var(--spacing-12);
    }
}

.about-text {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-4);
}

.about-heading {
    font-size: var(--font-size-xl);
    line-height: 1.6;
}

@media (min-width: 640px) {
    .about-heading {
        font-size: var(--font-size-2xl);
    }
}

@media (min-width: 768px) {
    .about-heading {
        font-size: var(--font-size-3xl);
    }
}

.highlight {
    background: linear-gradient(90deg, rgba(196, 255, 160, 0.4) 0%, rgba(196, 255, 160, 0.05) 100%);
    padding: 0 var(--spacing-1);
}

.underline-accent {
    border-bottom: 2px solid var(--color-primary);
}

.about-subtitle {
    font-size: var(--font-size-base);
    font-weight: 400;
    color: var(--color-secondary);
}

@media (min-width: 640px) {
    .about-subtitle {
        font-size: var(--font-size-lg);
    }
}

/* ============================================
   SKILLS SECTION
   ============================================ */
.skills-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--spacing-8);
}

@media (min-width: 768px) {
    .skills-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: var(--spacing-10);
    }
}

.skill-category {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-4);
}

.skill-category-title {
    font-size: var(--font-size-base);
    font-weight: 600;
    color: var(--color-primary);
    padding-bottom: var(--spacing-2);
    border-bottom: 1px solid var(--color-border);
}

.skill-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-2);
}

.skill-item {
    display: flex;
    align-items: flex-start;
    gap: var(--spacing-2);
    font-size: var(--font-size-sm);
    color: var(--color-secondary);
}

.skill-item::before {
    content: '•';
    color: var(--color-accent-dark);
    font-weight: bold;
    margin-top: 2px;
}

/* Badges */
.badges-container {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-2);
}

@media (min-width: 640px) {
    .badges-container {
        gap: var(--spacing-3);
    }
}

.badge {
    display: inline-flex;
    padding: var(--spacing-2) var(--spacing-3);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    font-size: var(--font-size-xs);
    font-weight: 500;
    color: var(--color-primary);
    transition: all var(--transition-fast);
    background: white;
}

@media (min-width: 640px) {
    .badge {
        font-size: var(--font-size-sm);
    }
}

.badge:hover {
    border-color: var(--color-accent-dark);
    background: rgba(196, 255, 160, 0.1);
}

/* ============================================
   PROJECTS SECTION
   ============================================ */
.projects-header {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-5);
    padding: var(--spacing-10) var(--spacing-4);
}

@media (min-width: 500px) {
    .projects-header {
        flex-direction: row;
        align-items: center;
        justify-content: space-between;
    }
}

@media (min-width: 640px) {
    .projects-header {
        padding: var(--spacing-10) var(--spacing-6);
    }
}

.projects-grid {
    display: grid;
    grid-template-columns: 1fr;
    border-top: 1px solid var(--color-border);
}

@media (min-width: 768px) {
    .projects-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

.project-card {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-4);
    padding: var(--spacing-4);
    transition: background var(--transition-fast);
}

@media (min-width: 640px) {
    .project-card {
        padding: var(--spacing-6);
        gap: var(--spacing-5);
    }
}

@media (min-width: 768px) {
    .project-card:nth-child(even) {
        border-left: 1px solid var(--color-border);
    }
}

.project-card:hover {
    background: var(--color-surface);
}

.project-image {
    width: 100%;
    aspect-ratio: 16/10;
    background: linear-gradient(135deg, #1a1a2e, #16213e);
    border-radius: var(--radius-lg);
    overflow: hidden;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: transform var(--transition-base);
}

.project-card:hover .project-image {
    transform: scale(1.02);
}

.project-image-placeholder {
    font-size: 3rem;
    color: rgba(255, 255, 255, 0.3);
}

.project-info {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-2);
    padding: 0 var(--spacing-2);
}

.project-title {
    font-size: var(--font-size-lg);
    font-weight: 500;
    color: var(--color-primary);
}

.project-description {
    font-size: var(--font-size-sm);
    color: var(--color-secondary);
    line-height: 1.6;
}

.project-meta {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-2);
    margin-top: var(--spacing-2);
}

.project-tag {
    font-size: var(--font-size-xs);
    padding: var(--spacing-1) var(--spacing-2);
    background: var(--color-surface);
    border-radius: var(--radius-sm);
    color: var(--color-secondary);
}

/* Clickable project cards */
a.project-card-link {
    text-decoration: none;
    color: inherit;
    cursor: pointer;
}

a.project-card-link:hover {
    background: var(--color-surface);
}

a.project-card-link:hover .project-title {
    color: var(--color-accent-dark);
}

/* ============================================
   EXPERIENCE SECTION
   ============================================ */
.experience-header {
    padding: var(--spacing-10) var(--spacing-4);
}

@media (min-width: 640px) {
    .experience-header {
        padding: var(--spacing-10) var(--spacing-6);
    }
}

.experience-list {
    border-top: 1px solid var(--color-border);
}

.experience-item {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-5);
    padding: var(--spacing-8) var(--spacing-4);
    border-bottom: 1px dashed var(--color-border);
}

@media (min-width: 640px) {
    .experience-item {
        padding: var(--spacing-10) var(--spacing-6);
    }
}

.experience-item:last-child {
    border-bottom: none;
}

.experience-header-row {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: space-between;
    gap: var(--spacing-4);
}

.experience-role {
    font-size: var(--font-size-lg);
    font-weight: 500;
}

.experience-meta {
    display: flex;
    align-items: center;
    gap: var(--spacing-2);
    padding: var(--spacing-2) var(--spacing-3);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    font-size: var(--font-size-sm);
}

.experience-indicator {
    width: 16px;
    height: 8px;
    border-radius: 2px;
    background: var(--color-primary);
}

.experience-indicator.past {
    background: var(--color-border);
}

.experience-points {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-2);
}

.experience-point {
    display: flex;
    align-items: flex-start;
    gap: var(--spacing-2);
    font-size: var(--font-size-base);
    color: var(--color-secondary);
}

.experience-point::before {
    content: '•';
    color: var(--color-accent-dark);
    font-weight: bold;
}

/* ============================================
   EDUCATION SECTION
   ============================================ */
.education-header {
    padding: var(--spacing-10) var(--spacing-4);
}

@media (min-width: 640px) {
    .education-header {
        padding: var(--spacing-10) var(--spacing-6);
    }
}

.education-timeline {
    position: relative;
    border-top: 1px solid var(--color-border);
    padding: var(--spacing-10) var(--spacing-4);
}

@media (min-width: 640px) {
    .education-timeline {
        padding: var(--spacing-10) 0;
    }

    .education-timeline::before {
        content: '';
        position: absolute;
        left: 16rem;
        top: 0;
        bottom: 0;
        width: 1px;
        background: var(--color-border);
    }
}

.education-item {
    position: relative;
    display: flex;
    flex-direction: column;
    gap: var(--spacing-4);
    margin-bottom: var(--spacing-8);
    padding-left: var(--spacing-8);
}

@media (min-width: 640px) {
    .education-item {
        flex-direction: row;
        align-items: flex-start;
        padding-left: 0;
        margin-bottom: var(--spacing-16);
    }
}

.education-item:last-child {
    margin-bottom: 0;
}

.education-date {
    position: relative;
    font-size: var(--font-size-base);
    color: var(--color-primary);
}

@media (min-width: 640px) {
    .education-date {
        width: 16rem;
        text-align: right;
        padding-right: var(--spacing-16);
    }
}

.education-date::before {
    content: '';
    position: absolute;
    left: -1.625rem;
    top: 0;
    width: 24px;
    height: 24px;
    border: 1px solid var(--color-border);
    border-radius: 50%;
    background: white;
}

@media (min-width: 640px) {
    .education-date::before {
        left: auto;
        right: -12px;
    }
}

.education-date::after {
    content: '';
    position: absolute;
    left: -1.125rem;
    top: 6px;
    width: 12px;
    height: 12px;
    background: var(--color-primary);
    border-radius: 50%;
}

@media (min-width: 640px) {
    .education-date::after {
        left: auto;
        right: 0;
    }
}

.education-content {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-2);
}

@media (min-width: 640px) {
    .education-content {
        flex: 1;
        padding-left: var(--spacing-16);
    }
}

.education-title {
    font-weight: 600;
}

.education-subtitle {
    color: var(--color-primary);
}

/* ============================================
   RESEARCH SECTION
   ============================================ */
.research-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-3);
}

.research-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-2);
    padding: var(--spacing-3) var(--spacing-4);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    transition: all var(--transition-fast);
}

.research-item:hover {
    border-color: var(--color-accent-dark);
    background: rgba(196, 255, 160, 0.05);
    transform: translateX(4px);
}

.research-item h4 {
    font-weight: 400;
}

.research-item svg {
    width: 24px;
    height: 24px;
    color: var(--color-secondary);
    transition: all var(--transition-fast);
}

.research-item:hover svg {
    transform: translateX(4px) rotate(45deg);
    color: var(--color-accent-dark);
}

/* ============================================
   CONTACT SECTION
   ============================================ */
.contact-content {
    text-align: center;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-8);
}

.contact-text {
    max-width: 32rem;
}

.contact-text h2 {
    font-size: var(--font-size-2xl);
    margin-bottom: var(--spacing-4);
}

.contact-links {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-4);
}

@media (min-width: 640px) {
    .contact-links {
        flex-direction: row;
        gap: var(--spacing-6);
    }
}

.contact-link {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-2);
    padding: var(--spacing-3) var(--spacing-5);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-full);
    font-weight: 500;
    transition: all var(--transition-fast);
}

.contact-link:hover {
    border-color: var(--color-accent-dark);
    background: rgba(196, 255, 160, 0.1);
    transform: translateY(-2px);
}

.contact-link svg {
    width: 18px;
    height: 18px;
}

/* ============================================
   FOOTER
   ============================================ */
footer {
    border-top: 1px solid var(--color-border);
    background: white;
}

.footer-content {
    max-width: 48rem;
    margin: 0 auto;
    padding: var(--spacing-4) var(--spacing-4);
    text-align: center;
}

@media (min-width: 768px) {
    .footer-content {
        padding: var(--spacing-6) var(--spacing-6);
    }
}

.footer-content p {
    font-size: var(--font-size-sm);
    color: var(--color-secondary);
}

/* ============================================
   UTILITIES
   ============================================ */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

/* Smooth scroll offset for fixed header */
section[id] {
    scroll-margin-top: 60px;
}

/* Focus states for accessibility */
a:focus-visible,
button:focus-visible {
    outline: 2px solid var(--color-accent-dark);
    outline-offset: 2px;
}

/* Selection color */
::selection {
    background: var(--color-accent);
    color: var(--color-primary);
}

/* Loading animation for images */
@keyframes shimmer {
    0% {
        background-position: -200% 0;
    }

    100% {
        background-position: 200% 0;
    }
}

.loading {
    background: linear-gradient(90deg,
            var(--color-surface) 25%,
            var(--color-border) 50%,
            var(--color-surface) 75%);
    background-size: 200% 100%;
    animation: shimmer 1.5s infinite;
}