:root {
    --bg-main: #141218;
    --bg-card: #2B2930;
    --accent-red: #F45C43;
    --accent-gradient: linear-gradient(90deg, #EB3349 0%, #F45C43 51.5%, #EB3349 100%);
    --font-primary: 'Poppins', sans-serif;
    --text-white: #FFFFFF;
    --text-muted: rgba(255, 255, 255, 0.7);
    --border-radius: 12px;
    --transition: 0.3s ease;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    -webkit-tap-highlight-color: transparent;
}

body {
    font-family: var(--font-primary);
    background-color: var(--bg-main);
    color: var(--text-white);
    line-height: 1.5;
    overflow-x: hidden;
    min-height: 100vh;
}

.app-container {
    max-width: 430px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    position: relative;
    padding-bottom: 80px; /* Space for sticky footer */
}

/* Header */
.header {
    padding: 16px 20px;
    position: sticky;
    top: 0;
    background-color: var(--bg-main);
    z-index: 100;
}

.header-top {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 12px;
}

.logo-container {
    background-color: var(--bg-card);
    padding: 6px 12px;
    border-radius: 8px;
}

.logo {
    height: 18px;
    vertical-align: middle;
}

.back-btn {
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
    opacity: 0.8;
}

.spacer {
    width: 40px; /* Balance back button */
}

.progress-container {
    width: 100%;
    height: 4px;
    background-color: var(--bg-card);
    border-radius: 2px;
    overflow: hidden;
}

.progress-bar {
    height: 100%;
    background-color: var(--accent-red);
    transition: width 0.4s ease-out;
}

/* Quiz Content Area */
.quiz-container {
    padding: 24px 20px;
    flex-grow: 1;
}

/* Transitions */
.step {
    animation: fadeIn 0.4s ease-out forwards;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.hidden {
    display: none !important;
}

/* Footer Control */
.footer {
    position: fixed;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 100%;
    max-width: 430px;
    padding: 16px 20px 24px;
    background: linear-gradient(180deg, rgba(20, 18, 24, 0) 0%, rgba(20, 18, 24, 0.95) 20%);
    z-index: 90;
}