:root {
    /* Color Palette */
    --primary-bg: #F0F8FF; /* AliceBlue */
    --card-bg: #FFFFFF;
    --primary-pink: #FFDAE9; /* Pale Pink */
    --primary-blue: #ADD8E6; /* Light Blue */
    --accent-blue: #87CEEB; /* Sky Blue */
    --accent-pink: #FFB6C1; /* Light Pink */
    
    --text-main: #333333;
    --text-muted: #666666;
    
    --success-color: #98FB98; /* Pale Green */
    --success-border: #32CD32;
    --error-color: #FFB6C1; /* Light Red/Pink for error background */
    --error-border: #FF6347;

    --btn-primary: #87CEEB;
    --btn-primary-hover: #00BFFF;
    
    --border-radius: 16px;
    --card-shadow: 0 10px 25px rgba(0, 0, 0, 0.05);
    
    --font-family: 'Outfit', sans-serif;
}

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

body {
    font-family: var(--font-family);
    background: linear-gradient(135deg, var(--primary-pink) 0%, var(--primary-blue) 100%);
    color: var(--text-main);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    overflow-x: hidden;
}

#app {
    width: 100%;
    max-width: 600px;
    min-height: 100vh;
    background-color: transparent;
    position: relative;
    display: flex;
    flex-direction: column;
}

@media (min-width: 600px) {
    #app {
        min-height: auto;
        height: 90vh;
        background-color: var(--card-bg);
        border-radius: var(--border-radius);
        box-shadow: var(--card-shadow);
        overflow: hidden;
    }
}

.screen {
    flex: 1;
    display: flex;
    flex-direction: column;
    padding: 2rem;
    transition: opacity 0.3s ease-in-out, transform 0.3s ease-in-out;
    opacity: 0;
    pointer-events: none;
    position: absolute; /* Stack screens */
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    overflow-y: auto;
}

.screen.active {
    opacity: 1;
    pointer-events: auto;
    position: relative; /* Let active screen take flow if needed, but for absolute stacking usually we keep absolute. Let's try relative for flow content. */
    position: absolute;
    z-index: 10;
}

.screen.hidden {
    display: none; /* Hide completely when not active to prevent scroll/interaction */
}

/* Start Screen */
#start-screen {
    justify-content: center;
    align-items: center;
    text-align: center;
    background: rgba(255,255,255,0.6);
    backdrop-filter: blur(10px);
}

#start-screen h1 {
    font-size: 2.5rem;
    color: var(--text-main);
    margin-bottom: 1rem;
    background: -webkit-linear-gradient(45deg, #FF69B4, #4169E1);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.subtitle {
    font-size: 1.1rem;
    color: var(--text-muted);
    margin-bottom: 3rem;
}

/* Buttons */
.primary-btn {
    padding: 1rem 3rem;
    font-size: 1.2rem;
    font-weight: 600;
    color: white;
    background: linear-gradient(90deg, #87CEEB, #FFB6C1);
    border: none;
    border-radius: 50px;
    cursor: pointer;
    box-shadow: 0 4px 15px rgba(135, 206, 235, 0.4);
    transition: transform 0.2s, box-shadow 0.2s;
}

.primary-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(135, 206, 235, 0.6);
}

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

/* Quiz Screen */
#quiz-screen {
    background-color: var(--card-bg);
}

.quiz-header {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-bottom: 2rem;
}

.icon-btn {
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
    border-radius: 50%;
    transition: background 0.2s;
    display: flex;
    align-items: center;
    justify-content: center;
}

.icon-btn:hover {
    background-color: var(--primary-bg);
}

.progress-container {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.progress-text {
    font-size: 0.9rem;
    color: var(--text-muted);
    text-align: right;
}

.progress-bar-bg {
    width: 100%;
    height: 8px;
    background-color: var(--primary-bg);
    border-radius: 10px;
    overflow: hidden;
}

.progress-bar-fill {
    height: 100%;
    background: linear-gradient(90deg, #FFB6C1, #87CEEB);
    width: 2%; /* Initial */
    transition: width 0.3s ease;
}

.question-card {
    flex: 1;
    display: flex;
    flex-direction: column;
    justify-content: flex-start; /* items top */
    overflow-y: auto;
}

#question-text {
    font-size: 1.3rem;
    margin-bottom: 1.5rem;
    line-height: 1.4;
    color: var(--text-main);
}

.options-container {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    margin-bottom: 2rem;
}

.option-btn {
    padding: 1rem;
    border: 2px solid var(--primary-bg);
    background-color: white;
    border-radius: 12px;
    text-align: left;
    font-size: 1rem;
    color: var(--text-main);
    cursor: pointer;
    transition: all 0.2s ease;
    font-family: inherit;
}

.option-btn:hover:not(:disabled) {
    border-color: var(--accent-blue);
    background-color: #F0FBFF;
}

.option-btn.selected {
    /* Base style for selected but not yet validated (conceptually) */
}

.option-btn.correct {
    background-color: var(--success-color);
    border-color: var(--success-border);
    color: #006400;
}

.option-btn.wrong {
    background-color: var(--error-color);
    border-color: var(--error-border);
    color: #8B0000;
    animation: shake 0.4s cubic-bezier(.36,.07,.19,.97) both;
}

.quiz-footer {
    display: flex;
    justify-content: space-between;
    margin-top: auto;
    padding-top: 1rem;
}

.nav-btn {
    padding: 0.8rem 1.5rem;
    border: none;
    border-radius: 8px;
    font-weight: 500;
    cursor: pointer;
    background-color: var(--primary-bg);
    color: var(--text-muted);
    transition: all 0.2s;
}

.nav-btn:hover:not(:disabled) {
    background-color: var(--accent-blue);
    color: white;
}

.nav-btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

/* Result Screen */
#result-screen {
    text-align: center;
    background: white;
}

.result-header {
    margin-bottom: 2rem;
}

.score-card {
    background: linear-gradient(135deg, #E0F7FA 0%, #E6E6FA 100%);
    padding: 2rem;
    border-radius: 20px;
    margin-top: 1rem;
    display: inline-block;
    width: 100%;
}

.score-display {
    font-size: 3rem;
    font-weight: 700;
    color: #4169E1;
}

.score-display .total {
    font-size: 1.5rem;
    color: var(--text-muted);
}

.wrong-answers-container {
    text-align: left;
    margin-top: 1rem;
    margin-bottom: 2rem;
    flex: 1; /* fills space */
    overflow-y: auto;
    /* Custom Scrollbar */
    padding-right: 5px;
}

/* Scrollbar styling */
.wrong-answers-container::-webkit-scrollbar {
    width: 6px;
}
.wrong-answers-container::-webkit-scrollbar-track {
    background: #f1f1f1; 
}
.wrong-answers-container::-webkit-scrollbar-thumb {
    background: #ccc; 
    border-radius: 3px;
}

.wrong-item {
    background-color: #FFF0F5;
    border-left: 4px solid var(--error-border);
    padding: 1rem;
    margin-bottom: 1rem;
    border-radius: 0 8px 8px 0;
}

.wrong-question-text {
    font-weight: 600;
    margin-bottom: 0.5rem;
    font-size: 0.95rem;
}

.correct-answer-display {
    color: #2E8B57;
    font-size: 0.9rem;
}

.highlight {
    font-weight: 700;
}

/* Animations */
@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); }
}