/* ============================================
   Materials Science Calculator - Modern CSS
   ============================================ */

/* CSS Variables */
:root {
    /* Colors */
    --color-primary: #3B82F6;
    --color-primary-dark: #2563EB;
    --color-primary-light: #60A5FA;
    --color-secondary: #10B981;
    --color-accent: #EF4444;

    --color-gray-50: #F9FAFB;
    --color-gray-100: #F3F4F6;
    --color-gray-200: #E5E7EB;
    --color-gray-300: #D1D5DB;
    --color-gray-400: #9CA3AF;
    --color-gray-500: #6B7280;
    --color-gray-600: #4B5563;
    --color-gray-700: #374151;
    --color-gray-800: #1F2937;
    --color-gray-900: #111827;

    /* Typography */
    --font-sans: 'Inter', 'Noto Sans JP', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', monospace;

    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    --spacing-3xl: 4rem;

    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-2xl: 1.5rem;

    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);

    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 200ms ease;
    --transition-slow: 300ms ease;
}

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

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-sans);
    font-size: 1rem;
    line-height: 1.6;
    color: var(--color-gray-800);
    background-color: var(--color-gray-50);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

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

/* ============================================
   Header
   ============================================ */
.header {
    position: sticky;
    top: 0;
    z-index: 100;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--color-gray-200);
}

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

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    text-decoration: none;
    color: var(--color-gray-900);
}

.logo-icon {
    width: 32px;
    height: 32px;
    color: var(--color-primary);
}

.logo-text {
    font-size: 1.125rem;
    font-weight: 600;
    letter-spacing: -0.025em;
}

.nav {
    display: flex;
    gap: var(--spacing-xl);
}

.nav-link {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--color-gray-600);
    text-decoration: none;
    transition: color var(--transition-fast);
}

.nav-link:hover {
    color: var(--color-primary);
}

/* ============================================
   Hero Section
   ============================================ */
.hero {
    padding: var(--spacing-3xl) 0;
    background: linear-gradient(135deg, var(--color-gray-50) 0%, #EEF2FF 100%);
    text-align: center;
}

.hero-title {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--color-gray-900);
    letter-spacing: -0.025em;
    margin-bottom: var(--spacing-md);
}

.hero-subtitle {
    font-size: 1.125rem;
    color: var(--color-gray-600);
    max-width: 600px;
    margin: 0 auto;
}

/* ============================================
   Sections
   ============================================ */
.section {
    padding: var(--spacing-3xl) 0;
}

.section-alt {
    background-color: white;
}

.section-header {
    text-align: center;
    margin-bottom: var(--spacing-2xl);
}

.section-title {
    font-size: 1.875rem;
    font-weight: 700;
    color: var(--color-gray-900);
    letter-spacing: -0.025em;
    margin-bottom: var(--spacing-sm);
}

.section-description {
    font-size: 1rem;
    color: var(--color-gray-500);
}

.category-title {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--color-gray-700);
    margin-bottom: var(--spacing-lg);
    padding-left: var(--spacing-sm);
    border-left: 3px solid var(--color-primary);
}

/* ============================================
   Card Grid
   ============================================ */
.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: var(--spacing-lg);
}

.card-grid-3 {
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
}

/* ============================================
   Cards
   ============================================ */
.card {
    display: flex;
    flex-direction: column;
    background: white;
    border-radius: var(--radius-xl);
    border: 1px solid var(--color-gray-200);
    padding: var(--spacing-lg);
    text-decoration: none;
    color: inherit;
    transition: all var(--transition-base);
    position: relative;
    overflow: hidden;
}

.card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: linear-gradient(90deg, var(--color-primary) 0%, var(--color-primary-light) 100%);
    opacity: 0;
    transition: opacity var(--transition-base);
}

.card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-xl);
    border-color: var(--color-primary-light);
}

.card:hover::before {
    opacity: 1;
}

.card-icon {
    width: 100%;
    height: 120px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--color-gray-50);
    border-radius: var(--radius-lg);
    margin-bottom: var(--spacing-md);
}

.card-icon-small {
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
    border-radius: var(--radius-md);
    margin-bottom: var(--spacing-md);
    flex-shrink: 0;
}

.card-icon-small svg {
    width: 24px;
    height: 24px;
    color: white;
}

.card-content {
    flex: 1;
}

.card-title {
    font-size: 1rem;
    font-weight: 600;
    color: var(--color-gray-900);
    margin-bottom: var(--spacing-xs);
}

.card-description {
    font-size: 0.875rem;
    color: var(--color-gray-500);
    line-height: 1.5;
}

.card-arrow {
    position: absolute;
    bottom: var(--spacing-lg);
    right: var(--spacing-lg);
    width: 24px;
    height: 24px;
    color: var(--color-gray-400);
    transition: all var(--transition-base);
}

.card:hover .card-arrow {
    color: var(--color-primary);
    transform: translateX(4px);
}

.card-compact {
    flex-direction: row;
    align-items: flex-start;
    gap: var(--spacing-md);
    padding: var(--spacing-md);
}

.card-compact .card-icon-small {
    margin-bottom: 0;
}

/* ============================================
   SVG Diagrams
   ============================================ */
.beam-diagram,
.rheology-diagram,
.slump-diagram {
    width: 100%;
    height: 100%;
}

.load-label,
.axis-label,
.tau-label,
.dimension-label {
    font-family: var(--font-sans);
    font-size: 14px;
    font-weight: 600;
    fill: var(--color-gray-700);
}

.tau-label {
    font-size: 12px;
    fill: var(--color-accent);
}

/* ============================================
   Footer
   ============================================ */
.footer {
    padding: var(--spacing-2xl) 0;
    background: var(--color-gray-900);
    color: var(--color-gray-400);
    text-align: center;
}

.footer-text {
    font-size: 0.875rem;
    margin-bottom: var(--spacing-xs);
}

.footer-note {
    font-size: 0.75rem;
    color: var(--color-gray-500);
}

/* ============================================
   Responsive
   ============================================ */
@media (max-width: 768px) {
    .header-content {
        flex-direction: column;
        height: auto;
        padding: var(--spacing-md) 0;
        gap: var(--spacing-md);
    }

    .nav {
        gap: var(--spacing-md);
    }

    .hero-title {
        font-size: 1.875rem;
    }

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

    .section-title {
        font-size: 1.5rem;
    }

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

/* ============================================
   Calculator Page Styles
   ============================================ */
.calc-container {
    display: grid;
    grid-template-columns: 1fr 1.5fr;
    gap: var(--spacing-xl);
    margin-top: var(--spacing-xl);
}

@media (max-width: 1024px) {
    .calc-container {
        grid-template-columns: 1fr;
    }
}

.calc-panel {
    background: white;
    border-radius: var(--radius-xl);
    border: 1px solid var(--color-gray-200);
    padding: var(--spacing-xl);
}

.calc-panel-title {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--color-gray-900);
    margin-bottom: var(--spacing-lg);
    padding-bottom: var(--spacing-sm);
    border-bottom: 2px solid var(--color-gray-100);
}

/* Form Elements */
.form-group {
    margin-bottom: var(--spacing-lg);
}

.form-label {
    display: block;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--color-gray-700);
    margin-bottom: var(--spacing-xs);
}

.form-input {
    width: 100%;
    padding: var(--spacing-sm) var(--spacing-md);
    font-size: 1rem;
    font-family: var(--font-sans);
    color: var(--color-gray-900);
    background: white;
    border: 1px solid var(--color-gray-300);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
}

.form-input:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

.form-select {
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' fill='none' viewBox='0 0 24 24' stroke='%236B7280'%3E%3Cpath stroke-linecap='round' stroke-linejoin='round' stroke-width='2' d='M19 9l-7 7-7-7'%3E%3C/path%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 0.75rem center;
    background-size: 1rem;
    padding-right: 2.5rem;
}

.form-hint {
    font-size: 0.75rem;
    color: var(--color-gray-500);
    margin-top: var(--spacing-xs);
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-lg);
    font-size: 0.875rem;
    font-weight: 500;
    font-family: var(--font-sans);
    border: none;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.btn-primary {
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
    color: white;
}

.btn-primary:hover {
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.btn-secondary {
    background: var(--color-gray-100);
    color: var(--color-gray-700);
}

.btn-secondary:hover {
    background: var(--color-gray-200);
}

.btn-block {
    width: 100%;
}

/* Results */
.result-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--spacing-md);
}

.result-item {
    background: var(--color-gray-50);
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
}

.result-label {
    font-size: 0.75rem;
    font-weight: 500;
    color: var(--color-gray-500);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: var(--spacing-xs);
}

.result-value {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--color-gray-900);
    font-family: var(--font-mono);
}

.result-unit {
    font-size: 0.875rem;
    font-weight: 400;
    color: var(--color-gray-500);
    margin-left: var(--spacing-xs);
}

/* Chart Container */
.chart-container {
    width: 100%;
    height: 400px;
    background: var(--color-gray-50);
    border-radius: var(--radius-lg);
    margin-top: var(--spacing-lg);
}

/* Stacked Chart Container (SFD/BMD分離表示用) */
.chart-container-stacked {
    width: 100%;
    height: 500px;
    min-height: 400px;
    background: var(--color-gray-50);
    border-radius: var(--radius-lg);
    margin-top: var(--spacing-lg);
    margin-bottom: var(--spacing-xl);
}

/* Formula Display */
.formula-box {
    background: var(--color-gray-800);
    color: white;
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    font-family: var(--font-mono);
    font-size: 0.875rem;
    overflow-x: auto;
    margin: var(--spacing-md) 0;
}

.formula-box > div:not(:last-child) {
    margin-bottom: 8px;
}

/* Back Link */
.back-link {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: 0.875rem;
    color: var(--color-gray-600);
    text-decoration: none;
    margin-bottom: var(--spacing-lg);
    transition: color var(--transition-fast);
}

.back-link:hover {
    color: var(--color-primary);
}

.back-link svg {
    width: 16px;
    height: 16px;
}

/* Utility Classes */
.text-left {
    text-align: left;
}

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

.mt-xl {
    margin-top: var(--spacing-xl);
}

.flex-row {
    display: flex;
    gap: 8px;
}

.w-80 {
    width: 80px;
}

.diagram-svg {
    width: 100%;
    max-width: 600px;
    display: block;
    margin: 0 auto;
}

.hidden {
    display: none;
}

.subsection-title {
    font-size: 1rem;
    font-weight: 600;
    margin-top: var(--spacing-xl);
    margin-bottom: var(--spacing-md);
}