/* Modern CSS Reset & Variables */
*, *::before, *::after {
    box-sizing: border-box;
}

:root {
    --color-bg: #0a0a0b;
    --color-surface: #141416;
    --color-surface-elevated: #1c1c1f;
    --color-border: #2a2a2e;
    --color-text: #fafafa;
    --color-text-secondary: #a1a1a6;
    --color-primary: #6366f1;
    --color-primary-hover: #818cf8;
    --color-accent: #22c55e;
    --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    --font-mono: 'SF Mono', Monaco, 'Cascadia Code', monospace;
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.5);
    --transition: 150ms ease;
}

html {
    font-family: var(--font-sans);
    background-color: var(--color-bg);
    color: var(--color-text);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    margin: 0;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Screen reader only */
.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;
}

/* Header & Navigation */
.header {
    position: sticky;
    top: 0;
    z-index: 100;
    background: rgba(10, 10, 11, 0.8);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--color-border);
}

.nav {
    max-width: 1200px;
    margin: 0 auto;
    padding: 1rem 1.5rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.logo {
    text-decoration: none;
    color: var(--color-text);
}

.logo h1 {
    font-size: 1.25rem;
    font-weight: 600;
    margin: 0;
    letter-spacing: -0.02em;
}

.nav-links {
    display: flex;
    list-style: none;
    margin: 0;
    padding: 0;
    gap: 0.5rem;
}

.nav-links a {
    display: block;
    padding: 0.5rem 1rem;
    color: var(--color-text-secondary);
    text-decoration: none;
    font-size: 0.9rem;
    border-radius: var(--radius-sm);
    transition: color var(--transition), background var(--transition);
}

.nav-links a:hover {
    color: var(--color-text);
    background: var(--color-surface);
}

.nav-toggle {
    display: none;
    padding: 0.5rem;
    background: none;
    border: none;
    cursor: pointer;
}

.hamburger {
    display: block;
    width: 24px;
    height: 2px;
    background: var(--color-text);
    position: relative;
}

.hamburger::before,
.hamburger::after {
    content: '';
    position: absolute;
    width: 24px;
    height: 2px;
    background: var(--color-text);
    left: 0;
}

.hamburger::before { top: -7px; }
.hamburger::after { top: 7px; }

/* Main Content */
.main {
    flex: 1;
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem 1.5rem;
}

/* Generator Section */
.generator {
    text-align: center;
    padding: 4rem 0;
}

.idea-container {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: 3rem 2rem;
    margin-bottom: 2rem;
    min-height: 160px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.idea {
    font-size: clamp(1.5rem, 4vw, 2.5rem);
    font-weight: 600;
    line-height: 1.3;
    margin: 0;
    letter-spacing: -0.02em;
    transition: opacity var(--transition);
}

.idea.loading {
    opacity: 0.5;
}

/* Buttons */
.actions {
    display: flex;
    gap: 0.75rem;
    justify-content: center;
    flex-wrap: wrap;
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.875rem 1.75rem;
    font-size: 1rem;
    font-weight: 500;
    font-family: inherit;
    border-radius: var(--radius-md);
    border: none;
    cursor: pointer;
    transition: all var(--transition);
    min-width: 120px;
}

.btn-primary {
    background: var(--color-primary);
    color: white;
    box-shadow: var(--shadow-sm);
}

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

.btn-primary:active {
    transform: translateY(0);
}

.btn-secondary {
    background: var(--color-surface);
    color: var(--color-text);
    border: 1px solid var(--color-border);
}

.btn-secondary:hover {
    background: var(--color-surface-elevated);
    border-color: var(--color-text-secondary);
}

/* History Section */
.history {
    margin-top: 3rem;
    padding-top: 2rem;
    border-top: 1px solid var(--color-border);
    display: none;
}

.history h3 {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--color-text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin: 0 0 1rem 0;
}

.history-list {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    justify-content: center;
}

.history-item {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    padding: 0.5rem 1rem;
    font-size: 0.875rem;
    color: var(--color-text-secondary);
    cursor: pointer;
    transition: all var(--transition);
    font-family: inherit;
    max-width: 300px;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.history-item:hover {
    background: var(--color-surface-elevated);
    color: var(--color-text);
    border-color: var(--color-text-secondary);
}

/* About Section */
.about {
    margin-top: 4rem;
    padding: 3rem;
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
}

.about h2 {
    font-size: 1.5rem;
    font-weight: 600;
    margin: 0 0 1rem 0;
    letter-spacing: -0.02em;
}

.about > p {
    color: var(--color-text-secondary);
    margin: 0 0 2rem 0;
    max-width: 720px;
}

.features {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
}

.feature {
    padding: 1.5rem;
    background: var(--color-bg);
    border-radius: var(--radius-md);
    border: 1px solid var(--color-border);
}

.feature h3 {
    font-size: 1rem;
    font-weight: 600;
    margin: 0 0 0.5rem 0;
    color: var(--color-primary-hover);
}

.feature p {
    font-size: 0.9rem;
    color: var(--color-text-secondary);
    margin: 0;
}

/* Guide Section */
.guide {
    margin-top: 4rem;
    padding: 3rem;
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
}

.guide h2 {
    font-size: 1.75rem;
    font-weight: 600;
    margin: 0 0 1rem 0;
    letter-spacing: -0.02em;
}

.guide-intro {
    color: var(--color-text-secondary);
    margin: 0 0 2.5rem 0;
    max-width: 720px;
    font-size: 1.1rem;
    line-height: 1.7;
}

.guide-content {
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

.guide-section {
    padding-bottom: 2rem;
    border-bottom: 1px solid var(--color-border);
}

.guide-section:last-child {
    padding-bottom: 0;
    border-bottom: none;
}

.guide-section h3 {
    font-size: 1.125rem;
    font-weight: 600;
    margin: 0 0 0.75rem 0;
    color: var(--color-text);
}

.guide-section p {
    color: var(--color-text-secondary);
    margin: 0;
    line-height: 1.7;
}

.guide-section a {
    color: var(--color-primary-hover);
    text-decoration: none;
}

.guide-section a:hover {
    text-decoration: underline;
}

/* Criteria Section */
.criteria {
    margin-top: 3rem;
    padding: 3rem;
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
}

.criteria h2 {
    font-size: 1.5rem;
    font-weight: 600;
    margin: 0 0 2rem 0;
    letter-spacing: -0.02em;
}

.criteria-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
}

.criteria-item {
    padding: 1.5rem;
    background: var(--color-bg);
    border-radius: var(--radius-md);
    border: 1px solid var(--color-border);
}

.criteria-item h3 {
    font-size: 1rem;
    font-weight: 600;
    margin: 0 0 0.5rem 0;
    color: var(--color-accent);
}

.criteria-item p {
    font-size: 0.9rem;
    color: var(--color-text-secondary);
    margin: 0;
    line-height: 1.6;
}

/* FAQ Section */
.faq {
    margin-top: 3rem;
    padding: 3rem;
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
}

.faq h2 {
    font-size: 1.5rem;
    font-weight: 600;
    margin: 0 0 2rem 0;
    letter-spacing: -0.02em;
}

.faq-list {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.faq-item {
    background: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    overflow: hidden;
}

.faq-item summary {
    padding: 1.25rem 1.5rem;
    font-weight: 500;
    cursor: pointer;
    list-style: none;
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: background var(--transition);
}

.faq-item summary::-webkit-details-marker {
    display: none;
}

.faq-item summary::after {
    content: '+';
    font-size: 1.25rem;
    color: var(--color-text-secondary);
    transition: transform var(--transition);
}

.faq-item[open] summary::after {
    transform: rotate(45deg);
}

.faq-item summary:hover {
    background: var(--color-surface-elevated);
}

.faq-item p {
    padding: 0 1.5rem 1.25rem;
    margin: 0;
    color: var(--color-text-secondary);
    line-height: 1.7;
}

/* Footer */
.footer {
    padding: 2rem 1.5rem;
    text-align: center;
    color: var(--color-text-secondary);
    font-size: 0.875rem;
    border-top: 1px solid var(--color-border);
}

.footer a {
    color: var(--color-text);
    text-decoration: none;
}

.footer a:hover {
    text-decoration: underline;
}

/* Toast Notifications */
.toast {
    position: fixed;
    bottom: 2rem;
    left: 50%;
    transform: translateX(-50%) translateY(100%);
    background: var(--color-surface-elevated);
    color: var(--color-text);
    padding: 0.875rem 1.5rem;
    border-radius: var(--radius-md);
    border: 1px solid var(--color-border);
    box-shadow: var(--shadow-lg);
    font-size: 0.9rem;
    opacity: 0;
    transition: all 300ms ease;
    z-index: 1000;
}

.toast.show {
    opacity: 1;
    transform: translateX(-50%) translateY(0);
}

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

    .nav-links {
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        flex-direction: column;
        background: var(--color-surface);
        border-bottom: 1px solid var(--color-border);
        padding: 1rem;
        gap: 0;
        display: none;
    }

    .nav-links.open {
        display: flex;
    }

    .nav-links a {
        padding: 0.875rem 1rem;
    }

    .generator {
        padding: 2rem 0;
    }

    .idea-container {
        padding: 2rem 1.5rem;
        min-height: 140px;
    }

    .about,
    .guide,
    .criteria,
    .faq {
        padding: 2rem 1.5rem;
    }

    .guide h2 {
        font-size: 1.5rem;
    }

    .guide-intro {
        font-size: 1rem;
    }

    .faq-item summary {
        padding: 1rem 1.25rem;
    }

    .faq-item p {
        padding: 0 1.25rem 1rem;
    }

    .actions {
        flex-direction: column;
    }

    .btn {
        width: 100%;
    }
}

/* Animations */
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.idea-container {
    animation: fadeIn 400ms ease;
}

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

button:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

/* Reduced motion */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* Print styles */
@media print {
    .header, .actions, .history, .footer {
        display: none;
    }

    .idea-container {
        border: none;
        padding: 0;
    }
}