/* ================================================
   AI Polynomial & Algebra Solver — Stylesheet v2.0
   ================================================ */

/* ---- CSS Custom Properties (Light Theme) ---- */
:root {
    --primary: #0284c7;
    --primary-dark: #0369a1;
    --secondary: #38bdf8;
    --bg-dark: #0f172a;
    --card-bg: #ffffff;
    --text-main: #1e293b;
    --text-muted: #64748b;
    --border-color: #e2e8f0;
    --surface: #f8fafc;
    --radius: 12px;
}

/* ---- Dark Mode Variables ---- */
body.dark-mode {
    --card-bg: #1e293b;
    --text-main: #e2e8f0;
    --text-muted: #94a3b8;
    --border-color: #334155;
    --surface: #0f172a;
}

/* ---- Container ---- */
.solver-container {
    max-width: 820px;
    margin: 0 auto;
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    color: var(--text-main);
}

/* ---- Header ---- */
.solver-header {
    background: linear-gradient(135deg, #0f172a 0%, #1e293b 100%);
    color: #ffffff;
    padding: 28px 32px;
    border-radius: var(--radius);
    margin-bottom: 20px;
    box-shadow: 0 10px 25px -5px rgba(15, 23, 42, 0.1);
    position: relative;
}

.solver-header .badge {
    display: inline-block;
    background: rgba(56, 189, 248, 0.15);
    color: var(--secondary);
    padding: 4px 12px;
    border-radius: 20px;
    font-size: 12px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: 10px;
}

.solver-header h1 {
    margin: 0 0 8px 0;
    font-size: 26px;
    font-weight: 700;
    letter-spacing: -0.5px;
    color: #ffffff !important;
}

.solver-header p {
    margin: 0;
    color: #94a3b8;
    font-size: 14px;
}

/* ---- Dark Mode Toggle ---- */
.dark-mode-btn {
    position: absolute;
    top: 16px;
    right: 16px;
    background: rgba(255, 255, 255, 0.1);
    border: 1px solid rgba(255, 255, 255, 0.2);
    color: #ffffff;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    font-size: 18px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s ease;
    line-height: 1;
    padding: 0;
}
.dark-mode-btn:hover {
    background: rgba(255, 255, 255, 0.2);
    transform: scale(1.1);
}

/* ---- Presets ---- */
.presets-wrapper {
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 16px;
}

.presets-label {
    font-size: 13px;
    font-weight: 600;
    color: var(--text-muted);
}

.preset-btn {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    color: var(--text-main);
    padding: 6px 12px;
    border-radius: 6px;
    font-size: 13px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s ease;
}
.preset-btn:hover {
    background: #f0f9ff;
    border-color: var(--primary);
    color: var(--primary-dark);
}
body.dark-mode .preset-btn:hover {
    background: #1e3a5f;
    color: var(--secondary);
}

/* ---- Input Card ---- */
.input-card {
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 24px;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.05), 0 2px 4px -1px rgba(0, 0, 0, 0.03);
    border: 1px solid var(--border-color);
    margin-bottom: 16px;
}

.input-group {
    display: flex;
    flex-direction: column;
    gap: 8px;
    margin-bottom: 16px;
}
.input-group label {
    font-size: 14px;
    font-weight: 600;
    color: var(--text-main);
}

.input-row {
    display: flex;
    gap: 10px;
}
.input-row input {
    flex: 1;
    padding: 12px 16px;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 16px;
    font-family: inherit;
    color: var(--text-main);
    background: var(--surface);
    transition: all 0.2s;
}
.input-row input:focus {
    outline: none;
    border-color: var(--primary);
    background: var(--card-bg);
    box-shadow: 0 0 0 3px rgba(2, 132, 199, 0.15);
}

/* ---- Primary Button ---- */
.primary-btn {
    background: var(--primary);
    color: #ffffff !important;
    border: none;
    padding: 12px 20px;
    border-radius: 8px;
    font-size: 15px;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.2s ease;
    white-space: nowrap;
}
.primary-btn:hover {
    background: var(--primary-dark);
}

/* ---- Keypad ---- */
.keypad-wrapper {
    margin-top: 12px;
}
.keypad-label {
    font-size: 12px;
    font-weight: 600;
    color: var(--text-muted);
    margin-bottom: 6px;
    display: block;
}
.math-keypad {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
}
.key-btn {
    background: var(--surface);
    border: 1px solid var(--border-color);
    color: var(--text-main);
    padding: 6px 10px;
    border-radius: 6px;
    font-size: 13px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.15s ease;
}
.key-btn:hover {
    background: #e2e8f0;
    border-color: var(--primary);
}
body.dark-mode .key-btn:hover {
    background: #334155;
}
.key-action {
    background: #fee2e2;
    border-color: #fca5a5;
    color: #991b1b;
}
body.dark-mode .key-action {
    background: #7f1d1d;
    border-color: #b91c1c;
    color: #fecaca;
}
.key-action:hover {
    background: #fecaca;
}
body.dark-mode .key-action:hover {
    background: #991b1b;
}

/* ---- Operation Selector ---- */
.operation-selector {
    display: flex;
    flex-wrap: wrap;
    gap: 16px;
    margin-top: 16px;
    padding-top: 14px;
    border-top: 1px solid var(--border-color);
}
.operation-selector label {
    font-size: 13px;
    font-weight: 600;
    color: var(--text-main);
    cursor: pointer;
}

/* ---- Preview ---- */
.preview-card {
    background: #f0f9ff;
    border-left: 4px solid var(--primary);
    padding: 14px 20px;
    border-radius: 0 8px 8px 0;
    margin-bottom: 24px;
}
body.dark-mode .preview-card {
    background: #0c2d48;
}
.preview-label {
    font-size: 12px;
    font-weight: 600;
    color: #0369a1;
    text-transform: uppercase;
    display: block;
    margin-bottom: 4px;
}
body.dark-mode .preview-label {
    color: var(--secondary);
}
.katex-preview {
    font-size: 18px;
    color: var(--text-main);
}

/* ---- Solution Card ---- */
.solution-card {
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 24px;
    border: 1px solid var(--border-color);
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.05);
    margin-bottom: 24px;
}
.solution-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    padding-bottom: 12px;
    border-bottom: 2px solid var(--border-color);
}
.solution-header h2 {
    margin: 0;
    font-size: 20px;
    font-weight: 700;
    color: var(--primary-dark);
}
body.dark-mode .solution-header h2 {
    color: var(--secondary);
}

.action-buttons {
    display: flex;
    gap: 8px;
}
.secondary-btn {
    background: var(--surface);
    color: var(--text-muted);
    border: 1px solid var(--border-color);
    padding: 8px 14px;
    border-radius: 6px;
    font-size: 13px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
}
.secondary-btn:hover {
    background: #e2e8f0;
    color: var(--text-main);
}
body.dark-mode .secondary-btn:hover {
    background: #334155;
}

/* ---- Steps Container ---- */
.steps-container {
    display: flex;
    flex-direction: column;
    gap: 18px;
}

/* ---- Step Card ---- */
.step-card {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 10px;
    padding: 18px 20px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.02);
}
.step-number {
    font-size: 12px;
    font-weight: 700;
    color: var(--primary);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: 6px;
}
body.dark-mode .step-number {
    color: var(--secondary);
}
.step-desc {
    font-size: 14px;
    color: #334155;
    margin-bottom: 10px;
    line-height: 1.5;
}
body.dark-mode .step-desc {
    color: #94a3b8;
}
.step-math {
    background: var(--surface);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 14px 18px;
    margin-top: 6px;
    overflow-x: auto;
    font-size: 17px;
    color: var(--text-main);
    text-align: center;
}

/* ---- Final Result Card ---- */
.final-result-card {
    background: linear-gradient(135deg, #f0fdf4 0%, #dcfce7 100%);
    border: 2px solid #22c55e;
    border-radius: 12px;
    padding: 20px 24px;
    margin-top: 8px;
}
body.dark-mode .final-result-card {
    background: linear-gradient(135deg, #052e16 0%, #14532d 100%);
    border-color: #16a34a;
}
.final-result-title {
    font-size: 16px;
    font-weight: 700;
    color: #15803d;
    margin-bottom: 8px;
}
body.dark-mode .final-result-title {
    color: #4ade80;
}
.final-result-card .step-math {
    background: #ffffff;
    border: 1px solid #86efac;
    color: #166534;
    font-weight: 700;
    font-size: 19px;
}
body.dark-mode .final-result-card .step-math {
    background: #064e3b;
    border-color: #16a34a;
    color: #bbf7d0;
}
.final-result-card .step-desc {
    color: #166534;
    font-size: 13px;
}
body.dark-mode .final-result-card .step-desc {
    color: #86efac;
}

/* ---- Graph Card ---- */
.graph-card {
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 20px 24px;
    border: 1px solid var(--border-color);
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.05);
    margin-bottom: 24px;
}
.graph-card h3 {
    margin: 0 0 12px 0;
    font-size: 17px;
    font-weight: 700;
    color: var(--primary-dark);
}
body.dark-mode .graph-card h3 {
    color: var(--secondary);
}
#polynomial-graph {
    width: 100%;
    min-height: 350px;
    border-radius: 8px;
    overflow: hidden;
}

/* ---- FAQ Section ---- */
.seo-faq-section {
    margin-top: 32px;
    padding-top: 24px;
    border-top: 2px solid var(--border-color);
}
.seo-faq-section h2 {
    font-size: 20px;
    font-weight: 700;
    color: var(--text-main);
    margin-bottom: 16px;
}
.faq-grid {
    display: flex;
    flex-direction: column;
    gap: 16px;
}
.faq-item {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 16px 20px;
}
.faq-item h3 {
    margin: 0 0 6px 0;
    font-size: 15px;
    color: var(--primary-dark);
}
body.dark-mode .faq-item h3 {
    color: var(--secondary);
}
.faq-item p {
    margin: 0;
    font-size: 14px;
    color: #475569;
    line-height: 1.5;
}
body.dark-mode .faq-item p {
    color: #94a3b8;
}

/* ---- SEO Guide ---- */
.seo-guide-content {
    color: var(--text-main);
}
.seo-guide-content h2, .seo-guide-content h3 {
    color: var(--text-main);
}
.seo-guide-content p, .seo-guide-content li {
    color: #475569;
    line-height: 1.6;
}
body.dark-mode .seo-guide-content p,
body.dark-mode .seo-guide-content li {
    color: #94a3b8;
}

/* ---- Utility ---- */
.hidden {
    display: none !important;
}

/* ---- Responsive ---- */
@media (max-width: 640px) {
    .solver-header {
        padding: 20px 18px;
    }
    .solver-header h1 {
        font-size: 20px;
        padding-right: 40px;
    }
    .input-row {
        flex-direction: column;
    }
    .primary-btn {
        width: 100%;
        text-align: center;
    }
    .operation-selector {
        gap: 10px;
    }
    .solution-header {
        flex-direction: column;
        gap: 10px;
        align-items: flex-start;
    }
    .action-buttons {
        width: 100%;
    }
    .secondary-btn {
        flex: 1;
        text-align: center;
    }
    .presets-wrapper {
        flex-direction: column;
        align-items: flex-start;
    }
    .step-math {
        font-size: 14px;
        padding: 10px 12px;
    }
    .final-result-card .step-math {
        font-size: 16px;
    }
    #polynomial-graph {
        min-height: 260px;
    }
}