:root {
    --bg: #070a1a;
    --bg2: #121735;
    --surface: rgba(255, 255, 255, 0.06);
    --surface-border: rgba(255, 255, 255, 0.14);
    --text: #f3f6ff;
    --muted: #b8c2de;
    --accent: #60a5fa; /* sky-400 */
    --accent2: #a78bfa; /* violet-400 */
    --ok: #22c55e; /* green-500 */
    --danger: #ef4444; /* red-500 */
    --ring: rgba(96, 165, 250, 0.38);
    --shadow: 0 20px 60px rgba(0, 0, 0, 0.45);
    --radius: 18px;
}

* {
    box-sizing: border-box;
}
html,
body {
    height: 100%;
}

body {
    margin: 0;
    font-family:
        Inter,
        system-ui,
        -apple-system,
        Segoe UI,
        Roboto,
        Arial,
        "Noto Sans",
        "Apple Color Emoji",
        "Segoe UI Emoji",
        "Segoe UI Symbol",
        sans-serif;
    color: var(--text);
    background: radial-gradient(
        1200px 800px at 10% 8%,
        #1c2150,
        #0e1130 50%,
        #070a1a 90%
    );
    overflow-x: hidden;
}

/* Decorative gradient blobs */
.bg {
    position: fixed;
    inset: 0;
    pointer-events: none;
    z-index: 0;
}
.blob {
    position: absolute;
    filter: blur(60px);
    opacity: 0.38;
    border-radius: 1000px;
    transform: translate(-50%, -50%);
}
.blob-1 {
    width: 520px;
    height: 520px;
    left: 12%;
    top: 16%;
    background:
        radial-gradient(circle at 60% 40%, #60a5fa, transparent 60%),
        radial-gradient(circle at 40% 70%, #a78bfa, transparent 60%);
}
.blob-2 {
    width: 600px;
    height: 520px;
    right: -8%;
    bottom: -4%;
    background:
        radial-gradient(circle at 50% 50%, #34d399, transparent 60%),
        radial-gradient(circle at 70% 40%, #60a5fa, transparent 60%);
}

/* Layout */
.container {
    position: relative;
    z-index: 1;
    max-width: 960px;
    margin: 0 auto;
    padding: 40px 18px 80px;
}

.screen {
    background: linear-gradient(
        180deg,
        rgba(255, 255, 255, 0.06),
        rgba(255, 255, 255, 0.03)
    );
    border: 1px solid var(--surface-border);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    padding: 24px;
}

.start-screen {
    text-align: center;
}

.hidden {
    display: none !important;
}

/* Brand */
.brand {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    margin-bottom: 10px;
}
.brand-mark {
    width: 52px;
    height: 52px;
    line-height: 52px;
    text-align: center;
    font-size: 28px;
    border-radius: 14px;
    background: linear-gradient(
        135deg,
        rgba(96, 165, 250, 0.25),
        rgba(167, 139, 250, 0.18)
    );
    border: 1px solid rgba(255, 255, 255, 0.14);
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
}
.brand-title {
    font-size: clamp(30px, 6vw, 54px);
    margin: 0;
    letter-spacing: 0.3px;
    background: linear-gradient(
        90deg,
        #fff,
        #c7d2fe 40%,
        #a5b4fc 70%,
        #93c5fd 100%
    );
    -webkit-background-clip: text;
    background-clip: text;
    color: transparent;
}

.subtitle {
    margin: 0 auto 14px;
    color: var(--muted);
    max-width: 720px;
}

.instructions {
    text-align: left;
    margin: 0 auto 22px;
    max-width: 760px;
    color: var(--muted);
    line-height: 1.5;
}

.btn {
    appearance: none;
    border: 1px solid rgba(255, 255, 255, 0.14);
    border-radius: 14px;
    padding: 12px 16px;
    color: var(--text);
    background: linear-gradient(
        180deg,
        rgba(255, 255, 255, 0.08),
        rgba(255, 255, 255, 0.03)
    );
    cursor: pointer;
    transition:
        transform 0.08s ease,
        box-shadow 0.2s,
        border-color 0.2s,
        background 0.2s,
        filter 0.2s;
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.25);
}
.btn:hover {
    transform: translateY(-1px);
    filter: brightness(1.06);
}
.btn:active {
    transform: translateY(0) scale(0.99);
}
.btn:focus-visible {
    outline: none;
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--ring);
}
.btn.primary {
    background: linear-gradient(
        135deg,
        rgba(96, 165, 250, 0.28),
        rgba(167, 139, 250, 0.18)
    );
}
.btn.secondary {
    background: linear-gradient(
        180deg,
        rgba(255, 255, 255, 0.08),
        rgba(255, 255, 255, 0.03)
    );
}

.topbar {
    display: flex;
    justify-content: space-between;

    align-items: center;

    margin-top: 6px;
    margin-bottom: 12px;

    color: var(--muted);
}

.chip {
    display: inline-flex;

    align-items: center;

    gap: 6px;
    padding: 6px 10px;
    border-radius: 999px;

    border: 1px solid rgba(255, 255, 255, 0.14);

    background: linear-gradient(
        180deg,
        rgba(255, 255, 255, 0.08),
        rgba(255, 255, 255, 0.03)
    );

    box-shadow: 0 6px 16px rgba(0, 0, 0, 0.22);
}

.chip-label {
    opacity: 0.8;

    font-size: 12px;
}

.chip-value {
    font-weight: 800;

    font-size: 12px;
}

/* Prompt */
.prompt {
    text-align: center;
    margin: 10px 0 18px;
    font-size: clamp(20px, 3.6vw, 28px);
}

/* Choices grid */
.choices {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 16px;
}

/* Cards */
.card {
    position: relative;
    border: 1px solid rgba(255, 255, 255, 0.14);
    border-radius: 18px;
    background: linear-gradient(
        180deg,
        rgba(255, 255, 255, 0.06),
        rgba(255, 255, 255, 0.03)
    );
    overflow: hidden;
    cursor: pointer;
    color: var(--text);
    min-height: 150px;
    text-align: center;
    transition:
        transform 0.14s ease,
        border-color 0.2s,
        box-shadow 0.2s,
        background 0.2s,
        filter 0.2s;
    box-shadow: 0 14px 36px rgba(0, 0, 0, 0.35);
}
.card:hover {
    transform: translateY(-3px);
    filter: brightness(1.05);
}
.card:focus-visible {
    outline: none;
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--ring);
}
.card .card-glow {
    position: absolute;
    inset: -40%;
    opacity: 0;
    background:
        radial-gradient(
            circle at 50% 0%,
            rgba(96, 165, 250, 0.25),
            transparent 60%
        ),
        radial-gradient(
            circle at 50% 100%,
            rgba(167, 139, 250, 0.22),
            transparent 60%
        );
    transition: opacity 0.2s ease;
    pointer-events: none;
}
.card:hover .card-glow {
    opacity: 1;
}
.card-inner {
    position: relative;
    padding: 18px 14px;
}

.card-label {
    font-size: clamp(18px, 3.2vw, 24px);
    font-weight: 800;
    letter-spacing: 0.2px;
}
.card-detail {
    margin-top: 8px;
    color: var(--muted);
    font-size: 14px;
    opacity: 0.95;
}

/* Selection and result states */
.card.selected {
    border-color: rgba(96, 165, 250, 0.85);
    box-shadow: 0 0 0 3px var(--ring);
}
.card.correct {
    border-color: rgba(34, 197, 94, 0.95);
    box-shadow:
        0 0 0 3px rgba(34, 197, 94, 0.28),
        0 20px 50px rgba(34, 197, 94, 0.18);
    animation: pop 0.22s ease;
    background: linear-gradient(
        180deg,
        rgba(34, 197, 94, 0.14),
        rgba(34, 197, 94, 0.06)
    );
}
.card.incorrect {
    border-color: rgba(239, 68, 68, 0.95);
    box-shadow:
        0 0 0 3px rgba(239, 68, 68, 0.28),
        0 20px 50px rgba(239, 68, 68, 0.18);
    animation: shake 0.28s ease;
    background: linear-gradient(
        180deg,
        rgba(239, 68, 68, 0.14),
        rgba(239, 68, 68, 0.06)
    );
}

/* Controls */
.controls {
    display: flex;
    gap: 10px;
    justify-content: center;
    margin-top: 18px;
}

/* Footer */
.footer {
    margin: 16px auto 32px;
    color: var(--muted);
    max-width: 960px;
    text-align: center;
    opacity: 0.9;
}

/* A11y */
.visually-hidden {
    position: absolute !important;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0 0 0 0);
    white-space: nowrap;
    border: 0;
}

/* Reveal state */
.revealed .card {
    cursor: default;
}
.revealed .card:hover {
    transform: none;
    filter: none;
}

/* Animations */
@keyframes pop {
    0% {
        transform: scale(1);
    }
    60% {
        transform: scale(1.04);
    }
    100% {
        transform: scale(1);
    }
}
@keyframes shake {
    0% {
        transform: translateX(0);
    }
    25% {
        transform: translateX(-6px);
    }
    50% {
        transform: translateX(5px);
    }
    75% {
        transform: translateX(-3px);
    }
    100% {
        transform: translateX(0);
    }
}

/* Responsive */

@media (max-width: 720px) {
    .choices {
        grid-template-columns: 1fr;
    }

    .card {
        min-height: 120px;
    }

    /* Pull stage down to avoid title overlap on short viewports */
    .stage {
        margin-top: 16vh !important;
    }
}

/* Slightly larger small screens: keep extra spacing under sky title */
@media (max-width: 900px) and (min-width: 721px) {
    .stage {
        margin-top: 12vh !important;
    }
}