:root {
    --calc-dock-h: 340px;
    --calc-dock-w: 480px;
    --tables-dock-w: 480px;
    --primary: #2563eb;
    --primary-hover: #1d4ed8;
    --bg-main: #f8fafc;
    --card-bg: #ffffff;
    --border-color: #e2e8f0;
    --text-main: #1e293b;
    --text-muted: #64748b;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--bg-main);
    color: var(--text-main);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.app-header {
    background-color: #ffffff;
    border-bottom: 1px solid var(--border-color);
    padding: 0.85rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: sticky;
    top: 0;
    z-index: 100;
}

.logo-area h1 {
    font-size: 1.5rem;
    font-weight: 800;
    letter-spacing: -0.5px;
    color: #0f172a;
}

.logo-area .domain-tag {
    color: var(--primary);
}

.subtitle {
    font-size: 0.85rem;
    color: var(--text-muted);
    font-weight: 500;
}

.header-controls {
    display: flex;
    gap: 0.75rem;
    align-items: center;
}

.header-btn {
    background-color: var(--primary);
    color: #ffffff;
    border: none;
    border-radius: 6px;
    padding: 0.5rem 1rem;
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    transition: background-color 0.15s ease;
}

.header-btn:hover {
    background-color: var(--primary-hover);
}

#page-wrapper {
    flex: 1;
    padding: 2rem;
    max-width: 900px;
    margin: 0 auto;
    width: 100%;
    transition: margin 0.15s ease, padding 0.15s ease;
}

body.snap-mode-right #page-wrapper {
    margin-right: var(--tables-dock-w, 480px);
    max-width: calc(100vw - var(--tables-dock-w, 480px) - 2rem);
}
body.snap-mode-left #page-wrapper {
    margin-left: var(--tables-dock-w, 480px);
    max-width: calc(100vw - var(--tables-dock-w, 480px) - 2rem);
}
body.calc-docked-right #page-wrapper {
    margin-right: var(--calc-dock-w, 480px);
    max-width: calc(100vw - var(--calc-dock-w, 480px) - 2rem);
}
body.calc-docked-left #page-wrapper {
    margin-left: var(--calc-dock-w, 480px);
    max-width: calc(100vw - var(--calc-dock-w, 480px) - 2rem);
}
body.calc-docked-bottom #page-wrapper {
    padding-bottom: calc(var(--calc-dock-h, 340px) + 2rem);
}

.card {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.05);
    overflow: hidden;
}

.card-header {
    background: #f1f5f9;
    border-bottom: 1px solid var(--border-color);
    padding: 1rem 1.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.topic-selector-group {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.topic-selector-group select {
    padding: 0.4rem 0.8rem;
    border-radius: 6px;
    border: 1px solid var(--border-color);
    background: #ffffff;
    font-weight: 500;
}

.stats-group {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.mastery-badge {
    background: #e2e8f0;
    color: #475569;
    padding: 0.35rem 0.75rem;
    border-radius: 9999px;
    font-size: 0.85rem;
    font-weight: 700;
}

.mastery-badge.mastered {
    background: #dcfce7;
    color: #15803d;
}

.session-stats {
    font-size: 0.85rem;
    color: var(--text-muted);
}

.reset-btn {
    background: none;
    border: none;
    font-size: 1.1rem;
    cursor: pointer;
    color: var(--text-muted);
}

.card-body {
    padding: 1.5rem;
}

.math-content {
    font-size: 1.1rem;
    line-height: 1.6;
    margin-bottom: 1.5rem;
}

.input-row {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-top: 1rem;
}

.input-row input {
    padding: 0.5rem 0.75rem;
    font-size: 1rem;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    width: 140px;
}

.input-row button {
    background-color: var(--primary);
    color: #ffffff;
    border: none;
    border-radius: 6px;
    padding: 0.5rem 1.25rem;
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
}

.banner {
    margin-top: 1.25rem;
    padding: 0.85rem 1.25rem;
    border-radius: 6px;
    font-weight: 600;
}

.banner.correct {
    background: #dcfce7;
    color: #166534;
    border: 1px solid #bbf7d0;
}

.banner.incorrect {
    background: #fee2e2;
    color: #991b1b;
    border: 1px solid #fecaca;
}

.stage-box {
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 1rem;
    margin-bottom: 1rem;
    background: #fafafa;
}

.stage-box.completed {
    border-color: #bbf7d0;
    background: #f0fdf4;
}

.stage-box.revealed {
    border-color: #fed7aa;
    background: #fff7ed;
}

.stage-header {
    display: flex;
    justify-content: space-between;
    font-weight: 700;
    font-size: 0.95rem;
}

.stage-hint {
    font-size: 0.85rem;
    color: var(--text-muted);
    margin-top: 0.35rem;
}

.revealed-msg {
    margin-top: 0.5rem;
    font-size: 0.85rem;
    color: #c2410c;
    font-weight: 600;
}

.solution-card {
    margin-top: 1.5rem;
    border-top: 2px dashed var(--border-color);
    padding-top: 1.5rem;
}

.graph-wrapper {
    margin: 1rem 0;
}

/* Floating / Docked Tables Window */
.floating-window {
    position: fixed;
    z-index: 10020;
    background: #ffffff;
    border: 1px solid #cbd5e1;
    border-radius: 8px;
    box-shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.2);
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

.floating-window.is-snapped-right {
    top: 0 !important;
    right: 0 !important;
    bottom: 0 !important;
    left: auto !important;
    width: var(--tables-dock-w, 480px) !important;
    height: 100vh !important;
    border-radius: 0 !important;
}

.floating-window.is-snapped-left {
    top: 0 !important;
    left: 0 !important;
    bottom: 0 !important;
    right: auto !important;
    width: var(--tables-dock-w, 480px) !important;
    height: 100vh !important;
    border-radius: 0 !important;
}

.floating-window.is-maximized {
    top: 0 !important;
    left: 0 !important;
    right: 0 !important;
    bottom: 0 !important;
    width: 100vw !important;
    height: 100vh !important;
    border-radius: 0 !important;
}

.window-titlebar {
    background: #0f172a;
    color: #ffffff;
    padding: 0.6rem 1rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    cursor: grab;
    user-select: none;
}

.window-controls button {
    background: transparent;
    border: none;
    color: #cbd5e1;
    font-size: 1rem;
    cursor: pointer;
    margin-left: 0.5rem;
}

.window-nav {
    display: flex;
    background: #f8fafc;
    border-bottom: 1px solid var(--border-color);
}

.window-tab-btn {
    flex: 1;
    padding: 0.5rem 0.25rem;
    background: none;
    border: none;
    border-bottom: 2px solid transparent;
    cursor: pointer;
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--text-muted);
}

.window-tab-btn.active {
    color: var(--primary);
    border-bottom-color: var(--primary);
    background: #ffffff;
}

.window-body {
    flex: 1;
    overflow-y: auto;
    padding: 1rem;
}

.tab-pane {
    display: none;
}

.tab-pane.active {
    display: block;
}

.stat-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.8rem;
}

.stat-table th, .stat-table td {
    border: 1px solid #cbd5e1;
    padding: 4px 6px;
    text-align: center;
}

.stat-table th {
    background: #f1f5f9;
    font-weight: 700;
}

.dock-resizer-strip {
    position: absolute;
    top: 0;
    bottom: 0;
    width: 10px;
    cursor: col-resize;
    z-index: 10025;
}

.is-snapped-right .dock-resizer-strip {
    left: -5px;
}

.is-snapped-left .dock-resizer-strip {
    right: -5px;
}

.window-resize-grip {
    position: absolute;
    bottom: 2px;
    right: 2px;
    width: 14px;
    height: 14px;
    cursor: nwse-resize;
    background: linear-gradient(135deg, transparent 50%, #94a3b8 50%);
}

/* Calculator Dock & Layout */
#calc-dock {
    position: fixed;
    z-index: 10010;
    background: #0f172a;
    border: 1px solid #334155;
    box-shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.3);
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

#calc-dock.dock-bottom {
    left: 0 !important;
    right: 0 !important;
    bottom: 0 !important;
    top: auto !important;
    height: var(--calc-dock-h, 340px) !important;
    border-radius: 0;
    border-top: 2px solid #3b82f6;
}

body.snap-mode-right #calc-dock.dock-bottom {
    right: var(--tables-dock-w, 480px) !important;
}
body.snap-mode-left #calc-dock.dock-bottom {
    left: var(--tables-dock-w, 480px) !important;
}

#calc-dock.dock-right {
    top: 0 !important;
    right: 0 !important;
    bottom: 0 !important;
    left: auto !important;
    width: var(--calc-dock-w, 480px) !important;
    height: 100vh !important;
    border-radius: 0;
}

#calc-dock.dock-left {
    top: 0 !important;
    left: 0 !important;
    bottom: 0 !important;
    right: auto !important;
    width: var(--calc-dock-w, 480px) !important;
    height: 100vh !important;
    border-radius: 0;
}

#calc-dock.dock-float {
    border-radius: 8px;
    width: 580px;
    height: 400px;
    top: 80px;
    left: 100px;
}

#calc-dock.dock-bottom #calc-dock-resizer {
    top: -5px;
    left: 0;
    right: 0;
    height: 10px;
    width: 100%;
    cursor: row-resize;
}

#calc-dock.dock-right #calc-dock-resizer {
    left: -5px;
    top: 0;
    bottom: 0;
    width: 10px;
    cursor: col-resize;
}

#calc-dock.dock-left #calc-dock-resizer {
    right: -5px;
    top: 0;
    bottom: 0;
    width: 10px;
    cursor: col-resize;
}

.calc-header {
    background: #0f172a;
    color: #ffffff;
    padding: 0.5rem 0.85rem;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    flex: 1 1 auto;
    min-height: 0;
}

.calc-header-top {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.calc-title {
    font-size: 0.85rem;
    font-weight: 700;
    color: #cbd5e1;
}

.calc-dock-controls button {
    background: transparent;
    border: none;
    color: #94a3b8;
    font-size: 1rem;
    cursor: pointer;
    margin-left: 0.4rem;
    transition: color 0.1s ease;
}

.calc-dock-controls button:hover,
.calc-dock-controls button.active {
    color: #60a5fa;
}

.calc-display-section {
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
    flex: 1 1 0px;
    min-height: 0;
}

.calc-history-list {
    background: #ffffff;
    border: 1px solid #cbd5e1;
    border-radius: 6px;
    padding: 0.4rem 0.6rem;
    flex: 1 1 auto !important;
    max-height: none !important;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.calc-history-row {
    color: #0f172a;
    font-size: 0.95rem;
    display: flex;
    align-items: center;
    gap: 0.4rem;
}

.calc-history-chip {
    cursor: pointer;
    background: #f1f5f9;
    padding: 2px 6px;
    border-radius: 4px;
}
.calc-history-chip:hover {
    background: #e2e8f0;
}

.calc-input-row {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    background: #ffffff;
    border: 1px solid #cbd5e1;
    border-radius: 6px;
    padding: 0.25rem 0.6rem;
    min-height: 44px;
}

.calc-mode-btn {
    background: #e2e8f0;
    border: 1px solid #cbd5e1;
    border-radius: 4px;
    font-size: 0.75rem;
    font-weight: 700;
    padding: 4px 8px;
    cursor: pointer;
}

#calc-mathfield {
    flex: 1;
    font-size: 1.4rem;
    border: none;
    outline: none;
}

/* Keypad Centering and Cluster Pods */
.calc-tray {
    background: #1e293b;
    padding: 0.6rem 0.85rem;
    flex: 0 0 auto !important;
    display: flex;
    justify-content: center;
}

.calc-keypad-container {
    display: flex;
    gap: 1.25rem;
    max-width: 820px;
    width: 100%;
    justify-content: center;
}

.calc-pod {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 6px;
    flex: 1;
}

.calc-key {
    background: #334155;
    color: #f8fafc;
    border: 1px solid #475569;
    border-radius: 6px;
    padding: 0.55rem 0.2rem;
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    user-select: none;
    transition: background 0.1s ease, transform 0.05s ease;
}

.calc-key:hover {
    background: #475569;
}
.calc-key:active {
    transform: scale(0.97);
}

.calc-key.num-key {
    background: #475569;
    font-size: 1.05rem;
}
.calc-key.num-key:hover {
    background: #64748b;
}

.calc-key.op-key {
    background: #1e40af;
    color: #ffffff;
    border-color: #3b82f6;
}
.calc-key.op-key:hover {
    background: #2563eb;
}

.calc-key.clear-key {
    background: #991b1b;
    color: #fef2f2;
    border-color: #ef4444;
}
.calc-key.clear-key:hover {
    background: #dc2626;
}

.calc-key.bank-btn {
    background: #b45309;
    color: #fffbeb;
    border-color: #f59e0b;
}
.calc-key.bank-btn:hover {
    background: #d97706;
}

.calc-key.nav-key {
    background: #1e293b;
    color: #cbd5e1;
}

.calc-key.backspace-key {
    background: #334155;
    color: #f87171;
}

.calc-key.eval-key {
    background: #15803d;
    color: #ffffff;
    border-color: #22c55e;
    font-weight: 700;
}
.calc-key.eval-key:hover {
    background: #16a34a;
}