:root {
    --primary: #D63031;
    --primary-dark: #b52b2b;
    --secondary: #FF7675;
    --accent: #00CEC9;
    --background: #1A0A0A;
    --surface: rgba(255, 255, 255, 0.05);
    --glass-border: rgba(255, 255, 255, 0.1);
    --text: #FFFFFF;
    --text-muted: rgba(255, 255, 255, 0.6);
    --success: #00CEC9;
    --error: #FF7675;
    --radius: 12px;
    --shadow: 0 8px 32px 0 rgba(0, 0, 0, 0.37);
}

body {
    margin: 0;
    padding: 0;
    font-family: 'Inter', system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background-color: var(--background);
    color: var(--text);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    overflow: hidden;
    background-image: radial-gradient(circle at 50% 50%, #2c1010 0%, #1a0a0a 100%);
}

#app {
    width: 100%;
    max-width: 600px;
    height: 100vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    padding: 20px;
    box-sizing: border-box;
}

.screen {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    width: 100%;
    height: 100%;
    transition: opacity 0.3s ease, transform 0.3s ease;
    opacity: 0;
    pointer-events: none;
    position: absolute;
    top: 0;
    left: 0;
    padding: 20px;
    box-sizing: border-box;
}

.screen.active {
    opacity: 1;
    pointer-events: all;
    transform: translateY(0);
    z-index: 10;
}

.screen.hidden {
    display: none;
}

.game-title {
    font-size: 3rem;
    font-weight: 800;
    color: var(--primary);
    text-transform: uppercase;
    text-shadow: 0 0 20px rgba(214, 48, 49, 0.5);
    margin-bottom: 40px;
    letter-spacing: 2px;
}

h3 {
    color: var(--text-muted);
    font-weight: 600;
    margin-bottom: 15px;
    text-transform: uppercase;
    font-size: 0.9rem;
    letter-spacing: 1px;
}

.btn {
    padding: 12px 24px;
    border-radius: var(--radius);
    border: none;
    cursor: pointer;
    font-weight: 600;
    font-size: 1rem;
    transition: all 0.2s ease;
    text-transform: uppercase;
    letter-spacing: 1px;
    font-family: inherit;
}

.btn-primary {
    background-color: var(--primary);
    color: white;
    box-shadow: 0 4px 15px rgba(214, 48, 49, 0.3);
}

.btn-primary:hover {
    background-color: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(214, 48, 49, 0.4);
}

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

.btn-outline {
    background: transparent;
    border: 2px solid var(--glass-border);
    color: var(--text-muted);
}

.btn-outline:hover {
    border-color: var(--primary);
    color: var(--text);
}

.btn-outline.active {
    background-color: var(--surface);
    border-color: var(--primary);
    color: var(--primary);
    box-shadow: 0 0 15px rgba(214, 48, 49, 0.1);
}

.btn-large {
    font-size: 1.2rem;
    padding: 16px 48px;
    margin-top: 40px;
    width: 100%;
    max-width: 300px;
}

.btn-group {
    display: flex;
    gap: 10px;
    margin-bottom: 30px;
    flex-wrap: wrap;
    justify-content: center;
}

.glass-panel {
    background: var(--surface);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius);
    padding: 24px;
    box-shadow: var(--shadow);
    width: 100%;
    max-width: 400px;
    display: flex;
    flex-direction: column;
    align-items: center;
}

.high-score-display {
    color: var(--text-muted);
    margin-top: 20px;
    font-size: 1rem;
}

/* Game HUD */
.hud {
    display: flex;
    justify-content: space-between;
    width: 100%;
    max-width: 500px;
    margin-bottom: 20px;
}

.stat-box {
    background: var(--surface);
    padding: 10px 20px;
    border-radius: var(--radius);
    border: 1px solid var(--glass-border);
    display: flex;
    flex-direction: column;
    align-items: center;
    min-width: 80px;
}

.stat-box .label {
    font-size: 0.7rem;
    color: var(--text-muted);
    text-transform: uppercase;
    margin-bottom: 4px;
}

.stat-box .value {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--accent);
}

/* Race Track */
.race-track-container {
    width: 100%;
    max-width: 500px;
    margin-bottom: 30px;
    position: relative;
}

.race-track {
    width: 100%;
    height: 40px;
    /* background: linear-gradient(90deg, transparent 50%, rgba(255,255,255,0.1) 50%); */
    /* background-size: 40px 100%; */
    border-bottom: 2px dashed var(--glass-border);
    position: relative;
    display: flex;
    align-items: flex-end;
}

.racer {
    font-size: 2rem;
    position: absolute;
    bottom: -5px;
    left: 0;
    transition: left 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
    filter: drop-shadow(0 0 5px rgba(0,0,0,0.5));
}

.finish-line {
    font-size: 2rem;
    position: absolute;
    right: 0;
    bottom: -5px;
    opacity: 0.8;
}

.progress-bar {
    width: 100%;
    height: 4px;
    background: var(--surface);
    border-radius: 2px;
    margin-top: 5px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--accent);
    width: 0%;
    transition: width 0.3s ease;
    box-shadow: 0 0 10px var(--accent);
}

/* Game Area */
.problem-display {
    font-size: 4rem;
    font-weight: 800;
    margin-bottom: 20px;
    color: var(--text);
    text-shadow: 0 4px 10px rgba(0,0,0,0.5);
}

.answer-input {
    width: 100%;
    background: rgba(0, 0, 0, 0.2);
    border: 2px solid var(--glass-border);
    border-radius: var(--radius);
    padding: 15px;
    font-size: 2rem;
    color: var(--text);
    text-align: center;
    outline: none;
    transition: border-color 0.2s ease;
    font-family: 'Inter', monospace;
}

.answer-input:focus {
    border-color: var(--accent);
    box-shadow: 0 0 15px rgba(0, 206, 201, 0.2);
}

.answer-input.correct {
    border-color: var(--success);
    color: var(--success);
    animation: pulse 0.3s ease;
}

.answer-input.incorrect {
    border-color: var(--error);
    color: var(--error);
    animation: shake 0.3s ease;
}

/* Results */
.results-box {
    width: 100%;
    margin-bottom: 30px;
}

.result-row {
    display: flex;
    justify-content: space-between;
    width: 100%;
    margin-bottom: 15px;
    font-size: 1.2rem;
    color: var(--text-muted);
}

.result-row:last-child {
    margin-bottom: 0;
}

.result-row .highlight {
    color: var(--text);
    font-weight: 700;
    font-size: 1.5rem;
}

/* Animations */
@keyframes shake {
    0%, 100% { transform: translateX(0); }
    25% { transform: translateX(-5px); }
    75% { transform: translateX(5px); }
}

@keyframes pulse {
    0% { transform: scale(1); }
    50% { transform: scale(1.05); }
    100% { transform: scale(1); }
}

/* Media Queries */
@media (max-width: 480px) {
    .game-title { font-size: 2rem; }
    .problem-display { font-size: 3rem; }
    .stat-box { min-width: 60px; padding: 5px 10px; }
    .stat-box .value { font-size: 1.2rem; }
}