📊 Cells — Premium Client-Side Spreadsheet Editor

A high-end, responsive spreadsheet web application built entirely on client-side technologies. Operating with zero server-side dependencies, Cells guarantees absolute private workflows, storing all sheet contents, typography configurations, custom tab colors, and histories directly on your local machine.

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✨ Primary Features

🏁 Excel-Parity Selection & Keyboard Navigation

• Marching Ants Clipboard: Copying ranges (Ctrl + C) paints a custom pulsing green dashed marching ants outline. Clears instantly on edit, deselect, or Escape.
• Excel Selection Contiguity: Full mouse dragging, Shift + Click range anchors, and Shift + Arrow selections are fully supported with visual boundaries.
• F2 Inline Focus: Tapping F2 focuses the inline cell editor, positioning the cursor right at the end of the text. Navigating and typing Alphanumeric keys immediately overwrites cell values.

📋 Custom Spatial Clipboard Tools & Series Autofill

• Autofill series handle: Dragging the cell bottom-right crosshair autofills repeating patterns, steps (linear regression for numbers like 10, 20 -> 30, 40), and copies styles or formulas.
• Spatial copy-paste operations: Split, vertically copy, or horizontally copy values by space separators or delimiters. Pasting repeating blocks into large ranges distributes patterns automatically.

🌐 Cross-Sheet Formulas & Autocomplete Suggestions

• Cross-Sheet calculations: Formulas resolve sheets case-insensitively (e.g. =Sheet2!A1+sHeEt3!B5).
• Safety checks: Supports recursive formulas, circular reference protection (#CIRC!), and evaluation depth recursion limits (#LIMIT!) to prevent thread locks.
• Suggestions panel: Toggling = inside the formula bar reveals a glassmorphic autocompleter. Injects formulas and focuses parameters selection ranges (A1:A10) instantly.

🎨 Curated Swatches, Themes, & Bilingual Typography

• Bilingual Font Cairo: Cairo Google Font matches Arabic and Latin text beautifully within spreadsheet cells. Supports custom local system font loading and font sizing (10px to 24px).
• Curated swatches: Right-clicking workbook tabs opens swatches to customize color strips. Features sheet duplication, step-by-step movement, and confirmation-guarded sheet sweeps.
• LTR/RTL Directions: Toggling per-sheet direction pivots layouts, row headers, resize margins, and autofill handles seamlessly.

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🚀 Newly Added Advanced Systems

⌨️ Interactive Keyboard Shortcuts Modal

• Discover and learn high-speed grid keystrokes using a beautiful glassmorphic modal box.
• Filter Search Bar: Type keywords (e.g. "copy") to immediately hide unrelated shortcuts in real-time.
• Global Access: Press ? (Shift + /) when not editing cells or click ❓ in the header actions.

🔍 Find and Replace Sliding Panel

• Slide-out panel matching Chart Studio (accordion-style).
• Advanced Filters: Match Case, Entire Cell, and Search All Sheets.
• Double Highlights: Matching cells light up with amber outlines (.search-match), and the active index hit glows in pulsing emerald (.search-match-active).
• Instant Click Focus: Matches render in a scrollable sidebar list. Clicking a row automatically switches sheets, scroll-focuses (scrollIntoView), and selects the matching cell.

🛡️ Workbook Auto-Recovery & Backup Timelines

• Intelligent Auto-Saves: Saves complete workbook state snapshots to localStorage every 30 seconds, skipping saves if state hashes match (saves disk space).
• timeline recovery list: View recovery timestamps, sheet count, and occupied cells.
• Manual Snapshots: Capture custom-named saves (e.g. "Before CSV parsing").
• FIFO limits: Rotating queues keep 10 automated and 5 manual saves.
• Durable restores: confirmation prompts hot-swap states and write to history so restores are undoable.

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⌨️ Keystroke Commands Guide

Keystroke	Scope	Visual Action
Tab / Shift+Tab	Grid Selection	Focuses cell Right / Left
Enter / Shift+Enter	Grid Selection	Focuses cell Down / Up
← ↑ ↓ → (Arrows)	Grid Selection	Navigates selection anchor
Shift + Arrows	Grid Selection	Expands selection range outline
Ctrl + A	Grid Selection	Selects entire worksheet grid
Ctrl + C	Clipboard	Copies selected range ( Marching Ants )
Ctrl + V	Clipboard	Pastes formulas (offset relative) / Styles
F2	Cell Editor	Starts inline cell editing
Esc	Cell Editor / Selection	Cancels edits / Clears copied ants borders
Ctrl + Z / Ctrl + Y	History State	Triggers Undo / Redo action
? (Shift + /)	Shortcuts Modal	Toggles Shortcuts Help Overlay
Ctrl + F	Search Panel	Toggles Find & Replace Sidebar
Ctrl + S	Backups Panel	Focuses Manual Snapshot save form

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🏃 Running the Application

Since Cells is 100% client-side and server-free, you can run the app offline on your machine with zero configuration:

1. Direct Double-Click: Open index.html in any modern web browser (Google Chrome, Firefox, Microsoft Edge, Safari) directly from your filesystem.
2. Local Dev Server: Alternatively, serve it locally using a simple HTTP server:

   npx serve .

   Or double-click and open the local file directly to enjoy lightning-fast, high-end private spreadsheets!