:root {
    --bg: #111827;
    --card: #1f2937;
    --text: #f9fafb;
    --text-muted: #9ca3af;
    --primary: #3b82f6;
    --success: #10b981;
    --danger: #ef4444;
    --border: #374151;
    --input-bg: #111827;
}

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

body {
    font-family: 'Plus Jakarta Sans', sans-serif;
    background: var(--bg);
    color: var(--text);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
}

.app-container {
    width: 100%;
    max-width: 500px;
}

header {
    margin-bottom: 24px;
}

header h1 {
    font-size: 1.8rem;
    margin-bottom: 8px;
}

header p {
    color: var(--text-muted);
    font-size: 0.95rem;
    line-height: 1.5;
}

.card {
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: 16px;
    padding: 24px;
    box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.5);
}

.grid-inputs {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
    margin-bottom: 24px;
}

.input-group label {
    display: block;
    font-size: 0.85rem;
    color: var(--text-muted);
    margin-bottom: 8px;
}

.input-wrapper {
    position: relative;
}

.prefix {
    position: absolute;
    left: 12px;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-muted);
}

input[type="number"] {
    width: 100%;
    background: var(--input-bg);
    border: 1px solid var(--border);
    color: white;
    padding: 12px 12px 12px 30px;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
}

input:focus {
    outline: 2px solid var(--primary);
    border-color: transparent;
}

/* Settings */
.settings-group {
    background: rgba(0, 0, 0, 0.2);
    padding: 16px;
    border-radius: 12px;
    margin-bottom: 24px;
}

.setting-row {
    margin-bottom: 16px;
}

.setting-row:last-child {
    margin-bottom: 0;
}

.setting-row label {
    display: block;
    font-size: 0.85rem;
    margin-bottom: 8px;
    font-weight: 600;
}

.toggle-pill {
    display: flex;
    background: var(--input-bg);
    padding: 4px;
    border-radius: 8px;
    gap: 4px;
}

.toggle-pill button {
    flex: 1;
    background: transparent;
    border: none;
    color: var(--text-muted);
    padding: 8px;
    border-radius: 6px;
    font-size: 0.85rem;
    cursor: pointer;
    font-weight: 500;
    transition: 0.2s;
}

.toggle-pill button.active {
    background: var(--card);
    color: white;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.3);
}

.help-text {
    font-size: 0.75rem;
    color: var(--text-muted);
    margin-top: 6px;
}

/* Result Box */
.result-box {
    background: var(--input-bg);
    border-radius: 12px;
    padding: 20px;
    text-align: center;
    margin-bottom: 24px;
    transition: 0.3s;
}

.result-box.pass {
    border: 1px solid rgba(16, 185, 129, 0.3);
    background: rgba(16, 185, 129, 0.1);
}

.result-box.fail {
    border: 1px solid rgba(239, 68, 68, 0.3);
    background: rgba(239, 68, 68, 0.1);
}

.verdict {
    font-size: 1.5rem;
    font-weight: 800;
    margin-bottom: 8px;
    letter-spacing: 1px;
}

.pass .verdict {
    color: var(--success);
}

.fail .verdict {
    color: var(--danger);
}

.math-explainer {
    font-size: 0.9rem;
    color: var(--text-muted);
    margin-bottom: 16px;
}

.status-bar {
    height: 8px;
    background: rgba(255, 255, 255, 0.1);
    border-radius: 4px;
    overflow: hidden;
}

.bar-fill {
    height: 100%;
    width: 0%;
    transition: 0.5s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

.pass .bar-fill {
    background: var(--success);
}

.fail .bar-fill {
    background: var(--danger);
}

/* CTA */
.cta-box {
    text-align: center;
    animation: fadeIn 0.4s ease;
}

.cta-box h3 {
    margin-bottom: 8px;
}

.cta-box p {
    font-size: 0.9rem;
    color: var(--text-muted);
    margin-bottom: 16px;
}

.action-btn {
    width: 100%;
    padding: 14px;
    border-radius: 10px;
    border: none;
    font-weight: 700;
    cursor: pointer;
    font-size: 1rem;
    transition: 0.2s;
}

#cta-pass .action-btn {
    background: var(--success);
    color: white;
}

#cta-fail .action-btn {
    background: var(--text);
    /* White/Grey */
    color: var(--bg);
}

.hidden {
    display: none !important;
}

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

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Modal */
.overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.8);
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
    z-index: 10;
}

.form-card {
    background: var(--card);
    padding: 30px;
    border-radius: 16px;
    width: 100%;
    max-width: 400px;
    position: relative;
    border: 1px solid var(--border);
}

.close-btn {
    position: absolute;
    top: 10px;
    right: 15px;
    background: none;
    border: none;
    color: var(--text-muted);
    font-size: 1.5rem;
    cursor: pointer;
}

.field {
    margin-bottom: 16px;
}

.field label {
    display: block;
    margin-bottom: 8px;
    font-size: 0.9rem;
}

.field input {
    width: 100%;
    padding: 12px;
    background: var(--input-bg);
    border: 1px solid var(--border);
    border-radius: 8px;
    color: white;
}

#submit-btn {
    width: 100%;
    padding: 14px;
    background: var(--primary);
    color: white;
    border: none;
    border-radius: 8px;
    font-weight: 700;
    cursor: pointer;
}

/* FAQ */
.faq-section {
    margin-top: 40px;
    border-top: 1px solid var(--border);
    padding-top: 30px;
}

.faq-section h3 {
    text-align: center;
    margin-bottom: 24px;
    font-size: 1.4rem;
}

.faq-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
}

.faq-item {
    background: rgba(255, 255, 255, 0.03);
    padding: 20px;
    border-radius: 12px;
    border: 1px solid var(--border);
}

.faq-item h4 {
    margin-bottom: 10px;
    color: var(--primary);
    font-size: 1rem;
}

.faq-item p {
    font-size: 0.9rem;
    color: var(--text-muted);
    line-height: 1.6;
}

@media(max-width: 600px) {

    .grid-inputs,
    .faq-grid {
        grid-template-columns: 1fr;
    }
}