:root {
    /* Colours */
    --color-text: #333;
    --color-text-light: #777;
    --accent: #4a5568;
    --color-bg: #fff;
    --color-bg-light: #f5f7fa;
    --color-border: #e0e0e0;
    --color-accent-light: rgba(74, 85, 104, 0.1);
    --color-overlay: rgba(0, 0, 0, 0.5);
    --robot-face-color: #fff;
    --hover-color: white;
    --color-success: #40c057;
    --color-warning: #f9a825;
    --color-warning-light: rgba(249, 168, 37, 0.1);
    --color-success-light: rgba(56, 161, 105, 0.1);
    --color-error: #DE5A59;

    /* Sizing variables */
    --border-radius: 5px;
    --border-radius-circle: 50%;
    --border-radius-square: 2px;
    --container-width: 950px;
    --spacing-xs: 0.5rem;
    --spacing-sm: 0.8rem;
    --spacing-md: 1.2rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;

    /* Robotto */
    --robot-scale: 60px;
    --robot-face-size: calc(var(--robot-scale) * 0.6);
    --robot-eye-size: calc(var(--robot-scale) * 0.1);
    --robot-eye-gap: calc(var(--robot-scale) * 0.15);
    --robot-mouth-width: calc(var(--robot-scale) * 0.33);
    --robot-mouth-height: calc(var(--robot-scale) * 0.12);
    --robot-face-radius: calc(var(--robot-scale) * 0.1);
    --robot-eye-margin-bottom: calc(var(--robot-scale) * 0.08);

    /* Typography variables */
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.85rem;
    --font-size-base: 0.95rem;
    --font-size-md: 1.1rem;
    --font-size-lg: 1.4rem;
    --font-size-xl: 1.8rem;
    --font-size-xxl: 2.2rem;

    /* Shadow variables */
    --shadow-sm: 0 2px 10px rgba(0, 0, 0, 0.03);
    --shadow-md: 0 4px 20px rgba(0, 0, 0, 0.05);
    --shadow-lg: 0 10px 30px rgba(0, 0, 0, 0.15);
}

@media (prefers-color-scheme: dark) {
    :root {
        --color-text: #d4d4d4;
        --color-text-light: #9a9a9a;
        --accent: #6e818d;
        --color-bg: #131415;
        --color-bg-light: #1a1a1a;
        --color-border: #2e2e2e;
        --color-accent-light: rgba(92, 107, 115, 0.08);
        --robot-face-color: #ebebeb;
        --color-overlay: rgba(0, 0, 0, 0.7);
        --color-success: #478954;
        --color-success-light: rgba(104, 211, 145, 0.1);
        --color-error: #b83131;
        --color-warning: #ffc107;
        --color-warning-light: rgba(255, 193, 7, 0.1);
        --hover-color: black;
        --shadow-sm: 0 2px 10px rgba(0, 0, 0, 0.2);
        --shadow-md: 0 4px 20px rgba(0, 0, 0, 0.3);
        --shadow-lg: 0 10px 30px rgba(0, 0, 0, 0.4);
    }
}

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

body {
    display: flex;
    justify-content: center;
    align-items: center;
    margin: 0;
    background-color: var(--color-bg-light);
    padding: 20px;
    min-height: 100vh;
    min-height: 100vh;
    color: var(--color-text);
    line-height: 1.6;
    font-family: ui-rounded, -apple-system, BlinkMacSystemFont, "SF Pro Display", "SF Pro Icons", "Helvetica Neue", Helvetica, Arial, sans-serif;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

a {
    color: var(--accent);
    text-decoration: underline;
    text-decoration-color: color-mix(in srgb, var(--accent), transparent 40%);
}

a:hover {
    text-decoration-color: var(--accent);
}

.app-container {
    width: 100%;
    max-width: var(--container-width);
}

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

.main-robot {
    margin: 0 auto var(--spacing-md);
    width: var(--robot-scale);
    height: var(--robot-scale);
}

.robot {
    display: flex;
    position: relative;
    justify-content: center;
    align-items: center;
    border-radius: 50%;
    background: var(--accent);
    width: 100%;
    height: 100%;
}

.robot-face {
    display: flex;
    position: relative;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    border-radius: var(--robot-face-radius);
    background: var(--robot-face-color);
    width: var(--robot-face-size);
    height: var(--robot-face-size);
}

.robot-eyes {
    display: flex;
    gap: var(--robot-eye-gap);
    margin-bottom: var(--robot-eye-margin-bottom);
}

.robot-eye {
    transition: transform 0.1s;
    border-radius: 50%;
    background: var(--accent);
    width: var(--robot-eye-size);
    height: var(--robot-eye-size);
}

.robot-mouth {
    border-radius: 2px 2px 10px 10px;
    background: var(--accent);
    width: var(--robot-mouth-width);
    height: var(--robot-mouth-height);
}

.page-title {
    margin-bottom: var(--spacing-xs);
    color: var(--accent);
    font-weight: 700;
    font-size: var(--font-size-xl);
}

.page-subtitle {
    margin-bottom: var(--spacing-lg);
    color: var(--color-text-light);
    font-weight: 400;
    font-size: var(--font-size-base);
}

.tools-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-xl);
}

.tool-card {
    display: flex;
    flex-direction: column;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
    box-shadow: var(--shadow-md);
    border-radius: var(--border-radius);
    background-color: var(--color-bg);
    padding: 0;
    height: 100%;
    overflow: hidden;
    text-decoration: none;
}

.tool-card:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-lg);
}

.tool-header {
    background-color: var(--color-accent-light);
    padding: var(--spacing-sm);
    text-align: center;
}

.tool-title {
    margin-bottom: 0;
    color: var(--accent);
    font-weight: 600;
    font-size: var(--font-size-md);
}

.tool-content {
    display: flex;
    flex-grow: 1;
    flex-direction: column;
    padding: var(--spacing-md);
}

.tool-description {
    margin-bottom: var(--spacing-md);
    color: var(--color-text);
    font-size: var(--font-size-sm);
    text-decoration: none;
}

.tool-preview {
    display: flex;
    flex-direction: column;
    justify-content: center;
    margin-top: auto;
    border-radius: var(--border-radius);
    background-color: var(--color-bg-light);
    padding: var(--spacing-sm);
    height: 100px;
    overflow: hidden;
    font-size: var(--font-size-xs);
}

/* A/B Test Calculator Preview */
.results-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    align-items: center;
    gap: var(--spacing-xs);
    height: 100%;
}

.result-card {
    display: flex;
    flex-direction: column;
    align-items: center;
    border-radius: var(--border-radius);
    background-color: var(--color-bg);
    padding: var(--spacing-xs);
}

.result-title {
    margin-bottom: 2px;
    color: var(--color-text-light);
    font-weight: 500;
    font-size: var(--font-size-xs);
}

.result-value {
    color: var(--accent);
    font-weight: 700;
    font-size: var(--font-size-md);
    line-height: 1;
}

.result-subtitle {
    color: var(--color-text-light);
    font-size: calc(var(--font-size-xs) * 0.85);
}

/* SRM Calculator Preview */
.verdict {
    margin-bottom: 0;
    border-radius: var(--border-radius);
    padding: var(--spacing-sm);
    font-weight: 600;
    font-size: var(--font-size-base);
    text-align: center;
}

.verdict.no-mismatch {
    background-color: var(--color-success-light);
    color: var(--color-success);
}

.verdict.possible-mismatch {
    background-color: var(--color-warning-light);
    color: var(--color-warning);
}

.verdict.significant-mismatch {
    background-color: var(--color-error-light);
    color: var(--color-error);
}

/* Stop Early Stopping Preview */
.dots-container {
    display: grid;
    grid-template-rows: repeat(6, 1fr);
    grid-template-columns: repeat(19, 1fr);
    align-self: center;
    gap: 2px;
    margin: 0 auto;
    width: 100%;
    height: 100%;
}

.dot {
    border-radius: var(--border-radius-circle);
    aspect-ratio: 1/1;
    width: 100%;
    height: auto;
}

.dot.green {
    background-color: var(--color-success);
}

.dot.red {
    border-radius: var(--border-radius-square);
    background-color: var(--color-error);
}

.app-footer {
    margin-top: var(--spacing-xl);
    color: var(--color-text-light);
    font-size: var(--font-size-sm);
    text-align: center;
}

.footer-text {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: var(--spacing-xs);
}

.footer-link {
    color: var(--accent);
}

.separator {
    opacity: 0.5;
    color: var(--color-text-light);
    user-select: none;
}

.heart {
    color: #d42e28;
}

.desktop-only {
    display: contents;
    /* Makes container "disappear" while children remain in the grid */
}

@media (max-width: 600px) {
    :root {
        --robot-scale: 50px;
    }

    .desktop-only {
        display: none;
    }

    .dots-container {
        gap: 3px;
    }

    .tool-preview {
        height: 105px;
    }

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