:root {
    /* Cyber Sky brand palette */
    --bg: #042231;
    --card: #08344b;
    --card2: #0c4060;
    --text: #eaf6f4;
    --muted: #8fb6c4;
    --primary: #00ddb1;
    --accent: #16c8d6;
    --success: #36d399;
    --error: #ff6b6b;
    --warning: #ffd166;
    --border: rgba(255, 255, 255, .1);
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: radial-gradient(circle at top right, rgba(0, 221, 177, .14), transparent 25%),
                radial-gradient(circle at bottom left, rgba(22, 200, 214, .12), transparent 25%),
                var(--bg);
    color: var(--text);
    min-height: 100vh;
    line-height: 1.6;
    padding: 24px;
}

.container {
    max-width: 980px;
    margin: auto;
}

.container-narrow {
    max-width: 520px;
}

.login-form {
    margin-top: 22px;
}

.login-form input {
    margin-top: 0;
    margin-bottom: 16px;
    font-size: 18px;
    text-align: center;
    font-family: inherit;
}

.hero, .panel, .card, .lesson {
    background: rgba(8, 52, 75, .92);
    border: 1px solid var(--border);
    border-radius: 18px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, .3);
}

.hero {
    padding: 24px;
    margin-bottom: 20px;
}

.hero h1 {
    margin: 0 0 8px;
    font-size: 32px;
}

.hero p {
    margin: 0;
    color: var(--muted);
}

.scorebar {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 12px;
    margin: 20px 0;
}

.panel {
    padding: 16px;
}

.label {
    font-size: 13px;
    color: var(--muted);
}

.value {
    font-size: 28px;
    font-weight: 700;
}

.progress {
    height: 12px;
    background: #0f1524;
    border-radius: 999px;
    overflow: hidden;
    margin-top: 10px;
}

.progress > div {
    height: 100%;
    width: 0;
    background: linear-gradient(90deg, var(--primary), var(--accent));
    transition: width .35s ease;
}

.brief {
    padding: 20px;
    margin-bottom: 20px;
}

.brief h2, .section-title {
    margin-top: 0;
}

.brief code, .chip {
    background: rgba(0, 221, 177, .12);
    border: 1px solid rgba(0, 221, 177, .3);
    padding: 2px 8px;
    border-radius: 999px;
    color: var(--primary);
}

.code-block {
    background: #0a0e1a;
    padding: 15px;
    direction: ltr;
    text-align: left;
    border-radius: 10px;
    font-family: 'Courier New', monospace;
    font-size: 14px;
    overflow-x: auto;
    margin: 15px 0;
    border: 1px solid var(--border);
}

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

.card {
    padding: 22px;
    position: relative;
    transition: all 0.2s ease;
}

.card h3 {
    margin: 0 0 14px;
    font-size: 18px;
}

.card p {
    margin: 0 0 12px;
}

/* Stacked questions (Challenge 1) */
.stack {
    display: flex;
    flex-direction: column;
    gap: 18px;
}

.num {
    position: absolute;
    left: 14px;
    top: 14px;
    background: var(--card2);
    border: 1px solid var(--border);
    width: 34px;
    height: 34px;
    border-radius: 999px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    color: var(--muted);
}

.pts {
    position: absolute;
    right: 14px;
    top: 14px;
    font-size: 12px;
    color: var(--primary);
    background: rgba(0, 221, 177, .12);
    border: 1px solid rgba(0, 221, 177, .3);
    padding: 4px 8px;
    border-radius: 999px;
}

.platform {
    margin-top: 30px;
    font-size: 14px;
    color: var(--muted);
}

.platform strong {
    display: block;
    color: var(--text);
    font-size: 17px;
}

/* Input + check button row */
.input-row {
    display: flex;
    gap: 10px;
    align-items: stretch;
    margin-top: 14px;
}

.input-row input {
    flex: 1;
    margin-top: 0;
}

.btn-check {
    flex-shrink: 0;
    padding: 14px 24px;
    white-space: nowrap;
}

input {
    width: 100%;
    margin-top: 12px;
    background: #0f1524;
    color: var(--text);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 14px 16px;
    font-size: 16px;
    direction: ltr;
    text-align: left;
    font-family: monospace;
}

input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(0, 221, 177, .2);
}

input:disabled {
    opacity: .7;
}

.actions {
    display: flex;
    gap: 12px;
    flex-wrap: wrap;
    margin: 20px 0;
}

.btn {
    border: 0;
    border-radius: 999px;
    padding: 14px 20px;
    font-size: 16px;
    font-weight: 700;
    cursor: pointer;
}

.btn-primary {
    background: linear-gradient(90deg, var(--primary), var(--accent));
    color: #09111f;
}

.btn-secondary {
    background: #0a3a54;
    color: var(--text);
    border: 1px solid var(--border);
}

/* Brand logo */
.brand-logo {
    display: block;
    height: 130px;
    width: auto;
    margin: 0 auto 10px;
}

.hero-logo {
    height: 52px;
    width: auto;
    margin-bottom: 12px;
}

.feedback {
    min-height: 24px;
    font-weight: 700;
    margin-top: 10px;
    font-size: 14px;
}

.ok {
    color: var(--success);
}

.bad {
    color: var(--error);
}

.correct {
    border: 2px solid var(--success);
    box-shadow: 0 0 0 3px rgba(54, 211, 153, .12);
}

.wrong {
    border: 2px solid var(--error);
    box-shadow: 0 0 0 3px rgba(255, 107, 107, .12);
    animation: shake 0.3s ease;
}

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

/* Celebration confetti */
.confetti-piece {
    position: fixed;
    top: -16px;
    width: 10px;
    height: 14px;
    border-radius: 2px;
    z-index: 9999;
    pointer-events: none;
    will-change: transform, opacity;
    animation: confetti-fall linear forwards;
}

@keyframes confetti-fall {
    0% { transform: translateY(-16px) rotateZ(0deg); opacity: 1; }
    100% { transform: translateY(105vh) rotateZ(720deg); opacity: 0; }
}

/* Completion banner pop */
#global-feedback.ok {
    text-align: center;
    font-size: 18px;
    margin-top: 16px;
    animation: pop 0.5s ease;
}

@keyframes pop {
    0% { transform: scale(0.6); opacity: 0; }
    60% { transform: scale(1.1); }
    100% { transform: scale(1); opacity: 1; }
}

.lessons {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 14px;
    margin-top: 18px;
}

.lesson {
    padding: 16px;
}

.lesson h4 {
    margin: 0 0 8px;
}

.lesson p {
    margin: 0;
    color: var(--muted);
}

.hint {
    display: block;
    margin-top: 8px;
    color: var(--warning);
    font-size: 12px;
}

a {
    color: var(--primary);
    text-decoration: none;
}

a:hover {
    text-decoration: underline;
}

table {
    width: 100%;
}

th {
    text-align: right;
}

@media (max-width: 700px) {
    .grid, .lessons, .scorebar {
        grid-template-columns: 1fr;
    }
    .hero h1 {
        font-size: 26px;
    }
    body {
        padding: 16px;
    }
    .input-row {
        flex-direction: column;
    }
    .btn-check {
        width: 100%;
    }
}