:root {
    --primary-color: #66bb6a;
    --primary-dark: #43a047;
    --accent-color: #ffa726;
    --accent-dark: #f57c00;
    --bg-color: #f1f8e9;
    --card-bg: #ffffff;
    --text-color: #2e7d32;
    --text-light: #607d8b;
    --danger-color: #ef5350;
    --success-color: #66bb6a;

    --font-main: "Inter", sans-serif;
    --font-display: "Outfit", sans-serif;

    --shadow-sm: 0 4px 6px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --radius-lg: 24px;
    --radius-md: 16px;
}

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

body {
    font-family: var(--font-main);
    background-color: var(--bg-color);
    color: var(--text-color);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    overflow: hidden;
}

.app-container {
    width: 100%;
    max-width: 480px;
    height: 100vh; /* Mobile full height */
    max-height: 900px;
    background-color: var(--bg-color);
    position: relative;
    display: flex;
    flex-direction: column;
}

@media (min-width: 481px) {
    .app-container {
        height: 90vh;
        border-radius: var(--radius-lg);
        box-shadow: var(--shadow-md);
        background-color: #fff;
        overflow: hidden;
    }
    .options-grid {
        grid-template-columns: 1fr 1fr;
    }
}

.screen {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    display: flex;
    flex-direction: column;
    padding: 2rem;
    transition:
        opacity 0.4s ease,
        transform 0.4s ease;
    opacity: 0;
    pointer-events: none;
    transform: scale(0.95);
}

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

.screen.hidden {
    display: none; /* Fully hide to prevent focus issues */
}

/* Common Components */
.content-card {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    padding: 2.5rem 2rem;
    text-align: center;
    box-shadow: var(--shadow-sm);
    margin: auto 0;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1.5rem;
    width: 100%;
}

.icon-container {
    font-size: 4rem;
    background: #e8f5e9;
    width: 100px;
    height: 100px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 0.5rem;
    animation: float 3s ease-in-out infinite;
}

h1,
h2 {
    font-family: var(--font-display);
    color: var(--text-color);
    line-height: 1.2;
}

h1 {
    font-size: 2rem;
}
h2 {
    font-size: 1.75rem;
}

p {
    color: var(--text-light);
    line-height: 1.6;
}

.primary-btn {
    background-color: var(--primary-color);
    color: white;
    border: none;
    padding: 1rem 2rem;
    font-size: 1.1rem;
    font-weight: 600;
    border-radius: 50px;
    cursor: pointer;
    width: 100%;
    transition:
        transform 0.2s,
        background-color 0.2s,
        box-shadow 0.2s;
    box-shadow: 0 4px 12px rgba(102, 187, 106, 0.3);
}

.primary-btn:hover {
    background-color: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: 0 6px 16px rgba(102, 187, 106, 0.4);
}

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

/* Start Screen */
.game-info {
    display: flex;
    gap: 1.5rem;
    justify-content: center;
    margin: 1rem 0;
}

.info-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text-color);
}

.info-item .icon {
    font-size: 1.5rem;
}

/* Difficulty Selector */
.difficulty-selector {
    width: 100%;
    margin: 1rem 0;
    text-align: center;
}

.difficulty-selector h3 {
    font-family: var(--font-display);
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-color);
    margin-bottom: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.difficulty-selector .options {
    display: flex;
    justify-content: center;
    gap: 1rem;
}

.difficulty-selector label {
    display: block;
    background: #e8f5e9;
    padding: 0.5rem 1rem;
    border-radius: 20px;
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text-color);
    cursor: pointer;
    border: 2px solid transparent;
    transition: all 0.2s ease;
}

.difficulty-selector input[type="radio"] {
    display: none; /* Hide the actual radio button */
}

.difficulty-selector input[type="radio"]:checked + label {
    background-color: var(--primary-color);
    color: white;
    border-color: var(--primary-dark);
}

.difficulty-selector label:hover {
    background-color: var(--primary-color);
    color: white;
}

/* Game Screen */
#game-screen {
    justify-content: flex-start;
    padding-top: 3rem;
}

.game-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    width: 100%;
    margin-bottom: 1.5rem;
}

.lives-container {
    display: flex;
    gap: 0.25rem;
}

.heart {
    font-size: 1.5rem;
    transition: transform 0.3s;
}

.heart.lost {
    filter: grayscale(1);
    opacity: 0.3;
    transform: scale(0.8);
}

.score-container {
    font-family: var(--font-display);
    font-weight: 700;
    font-size: 1.25rem;
    background: #fff;
    padding: 0.5rem 1rem;
    border-radius: 20px;
    box-shadow: var(--shadow-sm);
}

.timer-bar-container {
    width: 100%;
    height: 8px;
    background: #e0e0e0;
    border-radius: 4px;
    margin-bottom: 2rem;
    overflow: hidden;
}

.timer-bar {
    height: 100%;
    background: var(--accent-color);
    width: 100%;
    transition: width 0.1s linear;
    border-radius: 4px;
}

.timer-bar.warning {
    background: var(--danger-color);
}

.question-card {
    background: #fff;
    border-radius: var(--radius-lg);
    padding: 2rem;
    box-shadow: var(--shadow-sm);
    width: 100%;
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

#question-text {
    text-align: center;
    font-size: 1.4rem;
}

.options-grid {
    display: grid;
    gap: 1rem;
    width: 100%;
}

.option-btn {
    background: #f5f5f5;
    border: 2px solid transparent;
    padding: 1rem;
    border-radius: var(--radius-md);
    font-family: var(--font-main);
    font-size: 1rem;
    font-weight: 500;
    color: var(--text-color);
    cursor: pointer;
    transition: all 0.2s;
    text-align: left;
}

.option-btn:hover {
    background: #e8f5e9;
    border-color: var(--primary-color);
}

.option-btn.correct {
    background: var(--success-color);
    color: white;
    border-color: var(--success-color);
}

.option-btn.wrong {
    background: var(--danger-color);
    color: white;
    border-color: var(--danger-color);
}

/* Game Over Screen */
.final-score {
    display: flex;
    flex-direction: column;
    align-items: center;
}

#final-score-value {
    font-size: 4rem;
    font-weight: 800;
    color: var(--primary-color);
    line-height: 1;
}

.label {
    font-size: 1rem;
    color: var(--text-light);
    text-transform: uppercase;
    letter-spacing: 1px;
}

/* Animations */
@keyframes float {
    0% {
        transform: translateY(0px);
    }
    50% {
        transform: translateY(-10px);
    }
    100% {
        transform: translateY(0px);
    }
}

.shake {
    animation: shake 0.5s cubic-bezier(0.36, 0.07, 0.19, 0.97) both;
}

@keyframes shake {
    10%,
    90% {
        transform: translate3d(-1px, 0, 0);
    }
    20%,
    80% {
        transform: translate3d(2px, 0, 0);
    }
    30%,
    50%,
    70% {
        transform: translate3d(-4px, 0, 0);
    }
    40%,
    60% {
        transform: translate3d(4px, 0, 0);
    }
}

/* Responsive adjustments */
@media (max-width: 375px) {
    .content-card {
        padding: 2rem 1.5rem;
    }

    h1 {
        font-size: 1.8rem;
    }

    h2 {
        font-size: 1.5rem;
    }

    .game-info {
        gap: 1rem;
    }

    .difficulty-selector .options {
        gap: 0.5rem;
        flex-wrap: wrap; /* Allow wrapping on very small screens */
    }

    .difficulty-selector label {
        padding: 0.5rem 0.75rem;
    }
}