:root {
    /* Brand Colors (Theme: Modern dark-first) */
    --clr-primary: #8b5cf6;
    --clr-primary-hover: #7c3aed;
    --clr-success: #10b981;
    --clr-danger: #ef4444;
    --clr-warning: #f59e0b;
    --clr-info: #3b82f6;

    /* Light Theme Base */
    --clr-bg-app: #f8fafc;
    --clr-bg-card: #ffffff;
    --clr-border: #e2e8f0;
    --clr-border-focus: #cbd5e1;
    --clr-text-main: #0f172a;
    --clr-text-muted: #64748b;
    --clr-bg-code: #f1f5f9;

    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;

    --font-sans: 'Inter', system-ui, sans-serif;
    --font-mono: 'Fira Code', ui-monospace, monospace;
    
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
}

[data-theme="dark"] {
    --clr-bg-app: #020617;
    --clr-bg-card: #0f172a;
    --clr-border: #1e293b;
    --clr-border-focus: #334155;
    --clr-text-main: #f8fafc;
    --clr-text-muted: #94a3b8;
    --clr-bg-code: #1e293b;
    --shadow-md: 0 10px 15px -3px rgb(0 0 0 / 0.5), 0 4px 6px -4px rgb(0 0 0 / 0.5);
}

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

body {
    font-family: var(--font-sans);
    background-color: var(--clr-bg-app);
    color: var(--clr-text-main);
    line-height: 1.5;
    transition: background-color 0.3s, color 0.3s;
}

.app-layout {
    max-width: 1200px;
    margin: 0 auto;
    padding: 1.5rem;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Header */
.app-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 2rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid var(--clr-border);
}

.brand {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    color: var(--clr-primary);
}

.brand h1 {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--clr-text-main);
    letter-spacing: -0.025em;
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem 1rem;
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    font-weight: 500;
    font-family: inherit;
    cursor: pointer;
    transition: all 0.2s;
    border: 1px solid transparent;
}

.btn-secondary {
    background-color: var(--clr-bg-code);
    color: var(--clr-text-main);
    border-color: var(--clr-border);
}

.btn-secondary:hover {
    background-color: var(--clr-border);
}

.icon-btn {
    background: transparent;
    border: 1px solid var(--clr-border);
    color: var(--clr-text-main);
    width: 36px;
    height: 36px;
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all 0.2s;
}

.icon-btn:hover {
    background: var(--clr-bg-code);
}

/* Cards */
.card {
    background-color: var(--clr-bg-card);
    border: 1px solid var(--clr-border);
    border-radius: var(--radius-md);
    padding: 1.5rem;
    margin-bottom: 1.5rem;
    box-shadow: var(--shadow-sm);
}

.card h2 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 1.25rem;
    color: var(--clr-text-main);
}

/* Stats Grid */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
}

.stat-box {
    background-color: var(--clr-bg-code);
    padding: 1.25rem;
    border-radius: var(--radius-md);
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    border: 1px solid var(--clr-border);
    transition: transform 0.2s, box-shadow 0.2s;
}

.stat-box:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
    border-color: var(--clr-primary);
}

.stat-label {
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--clr-text-muted);
}

.stat-value {
    font-size: 1.75rem;
    font-weight: 700;
    font-family: var(--font-mono);
    color: var(--clr-primary);
}

.helper-text {
    font-size: 0.875rem;
    color: var(--clr-text-muted);
}

.mt-3 { margin-top: 1rem; }
.mb-2 { margin-bottom: 0.75rem; }

/* Breakpoints Visualizer */
.breakpoints-visualizer {
    display: flex;
    height: 8px;
    border-radius: 4px;
    background-color: var(--clr-bg-code);
    overflow: hidden;
    margin-bottom: 1.5rem;
    position: relative;
    border: 1px solid var(--clr-border);
}

.bp-segment {
    height: 100%;
    position: absolute;
    top: 0;
    border-right: 2px solid var(--clr-bg-card);
    transition: background-color 0.3s;
}
.bp-segment:last-child {
    border-right: none;
}
.bp-segment.active-bp {
    background-color: var(--clr-primary);
    box-shadow: 0 0 10px var(--clr-primary);
}

.current-bp-announcer {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-size: 0.875rem;
    font-weight: 500;
}

.badge-list {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.badge {
    padding: 0.25rem 0.75rem;
    border-radius: 99px;
    background-color: var(--clr-bg-code);
    font-family: var(--font-mono);
    font-size: 0.75rem;
    border: 1px solid var(--clr-border);
    transition: all 0.2s;
}

.badge.active {
    background-color: var(--clr-primary);
    color: white;
    border-color: var(--clr-primary);
}

/* Custom Grid */
.custom-grid {
    display: grid;
    grid-template-columns: 1fr 1.5fr;
    gap: 1.5rem;
}

@media (max-width: 900px) {
    .custom-grid {
        grid-template-columns: 1fr;
    }
}

/* Form Styles */
.input-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    margin-bottom: 1.25rem;
}

.input-group label {
    font-size: 0.875rem;
    font-weight: 500;
}

.input-group input {
    width: 100%;
    padding: 0.75rem 1rem;
    border-radius: var(--radius-sm);
    border: 1px solid var(--clr-border);
    background-color: var(--clr-bg-app);
    color: var(--clr-text-main);
    font-family: var(--font-mono);
    font-size: 0.875rem;
    transition: border-color 0.2s;
    outline: none;
}

.input-group input:focus {
    border-color: var(--clr-primary);
}

.mq-result-box {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1.25rem;
    border-radius: var(--radius-md);
    background-color: var(--clr-bg-code);
    border: 1px solid var(--clr-border);
    transition: all 0.3s;
}

.mq-result-box.is-match {
    background-color: rgba(16, 185, 129, 0.1);
    border-color: var(--clr-success);
}

.mq-result-box.is-not-match {
    background-color: rgba(239, 68, 68, 0.1);
    border-color: var(--clr-danger);
}

.mq-status {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.is-match .mq-status {
    background-color: var(--clr-success);
    color: white;
}
.is-not-match .mq-status {
    background-color: var(--clr-danger);
    color: white;
}

.mq-text strong {
    display: block;
    font-size: 1rem;
    margin-bottom: 0.25rem;
}
.is-match .mq-text strong { color: var(--clr-success); }
.is-not-match .mq-text strong { color: var(--clr-danger); }

.mq-text p {
    font-size: 0.875rem;
    color: var(--clr-text-muted);
}

.bool-true { color: var(--clr-success); font-family: var(--font-mono); font-weight: 600; }
.bool-false { color: var(--clr-danger); font-family: var(--font-mono); font-weight: 600; }

/* Container Queries Demo */
.resizable-container-wrapper {
    width: 100%;
    padding: 1rem;
    border: 1px dashed var(--clr-border-focus);
    border-radius: var(--radius-md);
    background: repeating-linear-gradient(
        45deg,
        var(--clr-border),
        var(--clr-border) 10px,
        var(--clr-bg-card) 10px,
        var(--clr-bg-card) 20px
    );
}

.resizable-box {
    /* Critical for container queries */
    container-type: inline-size;
    container-name: demo;
    /* Resizable */
    resize: horizontal;
    overflow: hidden;
    min-width: 200px;
    max-width: 100%;
    height: auto;
    background: var(--clr-panel);
    border: 2px solid var(--clr-primary);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-md);
    background-color: var(--clr-bg-card);
}

.cq-content {
    padding: 1.5rem;
    background-color: var(--clr-bg-card);
    height: 100%;
}

.cq-stats {
    background-color: var(--clr-primary);
    color: white;
    padding: 0.5rem 1rem;
    border-radius: var(--radius-sm);
    display: inline-block;
    font-family: var(--font-mono);
    font-size: 0.75rem;
    margin-bottom: 1rem;
}

.cq-cards {
    display: grid;
    /* Default behavior: Mobile stack */
    grid-template-columns: 1fr;
    gap: 1rem;
}

.cq-card {
    background-color: var(--clr-bg-code);
    border: 1px solid var(--clr-border);
    padding: 2rem;
    text-align: center;
    border-radius: var(--radius-sm);
    font-weight: 700;
    font-size: 1.5rem;
    color: var(--clr-text-muted);
    transition: all 0.3s;
}

/* CONTAINER QUERIES STYLES */
@container demo (min-width: 400px) {
    .cq-cards {
        grid-template-columns: 1fr 1fr;
    }
    .cq-content {
        background-color: rgba(59, 130, 246, 0.05); /* Info tint */
    }
    .cq-card {
        color: var(--clr-info);
        border-color: rgba(59, 130, 246, 0.3);
    }
    .cq-stats::after { content: " (min-width: 400px)"; }
}

@container demo (min-width: 600px) {
    .cq-cards {
        grid-template-columns: 1fr 1fr 1fr;
    }
    .cq-content {
        background-color: rgba(16, 185, 129, 0.05); /* Success tint */
    }
    .cq-card {
        color: var(--clr-success);
        border-color: rgba(16, 185, 129, 0.3);
    }
    .cq-stats::after { content: " (min-width: 600px)"; }
}

/* Toast */
.toast {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    background-color: var(--clr-text-main);
    color: var(--clr-bg-card);
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius-sm);
    font-weight: 500;
    font-size: 0.875rem;
    box-shadow: var(--shadow-md);
    transition: opacity 0.3s, transform 0.3s;
    z-index: 100;
}
.toast.hidden {
    opacity: 0;
    pointer-events: none;
    transform: translateY(10px);
}