* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: var(--font-sans);
    -webkit-tap-highlight-color: transparent;
}

:root {
    --background: oklch(1 0 0);
    --foreground: oklch(0.145 0 0);
    --card: oklch(1 0 0);
    --primary: oklch(0.205 0 0);
    --primary-foreground: oklch(0.985 0 0);
    --secondary: oklch(0.97 0 0);
    --muted: oklch(0.97 0 0);
    --accent: oklch(0.97 0 0);
    --muted-foreground: oklch(0.556 0 0);
    --border: oklch(0.922 0 0);
    --input: oklch(0.922 0 0);
    --ring: oklch(0.708 0 0);
    --destructive: oklch(0.577 0.245 27.325);
    --success: oklch(0.6 0.16 145);

    --brand: var(--foreground);
    --brand-foreground: var(--background);

    --font-sans: "Plus Jakarta Sans", ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;

    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.625rem;
    --radius-xl: 0.875rem;
    --radius-full: 9999px;

    --space-xs: 4px;
    --space-sm: 8px;
    --space-md: 16px;
    --space-lg: 24px;
    --space-xl: 40px;
}

[data-theme="dark"] {
    --background: oklch(0.145 0 0);
    --foreground: oklch(0.985 0 0);
    --card: oklch(0.205 0 0);
    --primary: oklch(0.922 0 0);
    --primary-foreground: oklch(0.205 0 0);
    --secondary: oklch(0.269 0 0);
    --muted: oklch(0.269 0 0);
    --accent: oklch(0.269 0 0);
    --muted-foreground: oklch(0.708 0 0);
    --border: oklch(1 0 0 / 10%);
    --input: oklch(1 0 0 / 10%);
    --ring: oklch(0.556 0 0);
    --destructive: oklch(0.704 0.191 22.216);
    --success: oklch(0.75 0.18 145);
}

* {
    transition: background-color 0.2s ease, border-color 0.2s ease, color 0.2s ease;
}

body {
    background-color: var(--background);
    color: var(--foreground);
    display: flex;
    flex-direction: column;
    justify-content: center;
    min-height: 100vh;
}

.app-header {
    position: absolute;
    top: var(--space-md);
    right: var(--space-md);
    display: flex;
    align-items: center;
    gap: var(--space-xs);
}

#lang-toggle {
    font-weight: 500;
    font-size: 0.75rem;
}

.theme-toggle {
    background: transparent;
    border: none;
    color: var(--foreground);
    cursor: pointer;
    min-width: 36px;
    min-height: 36px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-lg);
}

@media (hover: hover) and (pointer: fine) {
    .theme-toggle:hover {
        background: var(--accent);
    }
}

.theme-toggle:active {
    transform: translateY(1px);
}

.hidden {
    display: none !important;
}

.app-main {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: var(--space-lg);
    max-width: 600px;
    margin: 0 auto;
    width: 100%;
}

.challenge-section {
    text-align: center;
    margin-bottom: var(--space-xl);
    width: 100%;
}

.challenge-label {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--muted-foreground);
    margin-bottom: var(--space-sm);
}

.challenge-display {
    font-size: 4rem;
    font-weight: 600;
    line-height: 1.2;
    min-height: 120px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.options-section {
    width: 100%;
}

.options-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-sm);
    width: 100%;
    max-width: 320px;
    margin: 0 auto;
}

.option-btn {
    background-color: var(--card);
    color: var(--foreground);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: var(--space-sm) var(--space-md);
    min-height: 40px;
    font-size: 0.875rem;
    font-weight: 600;
    cursor: pointer;
}

@media (hover: hover) and (pointer: fine) {
    .option-btn:hover {
        background-color: var(--accent);
        border-color: var(--ring);
    }
}

.option-btn:active {
    transform: translateY(1px);
}

.option-btn.correct {
    background-color: color-mix(in oklch, var(--success) 10%, transparent);
    border-color: var(--success);
    color: var(--success);
}

.option-btn.incorrect {
    background-color: color-mix(in oklch, var(--destructive) 10%, transparent);
    border-color: var(--destructive);
    color: var(--destructive);
}

@media (max-width: 480px) {
    .challenge-display {
        font-size: 3.25rem;
    }

    .option-btn {
        padding: var(--space-sm) var(--space-xs);
        font-size: 0.875rem;
    }
}