# Projects

A TunnelCAD project is the top-level container for all tunnel monitoring data. Each project is stored as a single `.tun` file (XML-based) and contains one or more **tunnel alignments**, plus shared **style libraries** for section lines and alignment display.

## Project structure

Every project holds:

- **Tunnel alignments** -- each alignment is fully self-contained with its own alignment geometry, line definitions, template line definitions, templates, station definitions, cross-sections, and volume definitions.
- **Section line style library** -- shared styles that control how measured and template lines are drawn across all tunnels.
- **Alignment style library** -- shared styles for alignment display on the alignment canvas.
- **Project-level units** -- angular units, station format, and decimal-place settings that apply to the entire project.

## Creating and opening projects

### New project

Select **File > New Project** (or press `Ctrl+N`) to create a blank project. The new project opens in a new tab with a default empty tunnel alignment ready for configuration.

### Open existing project

Select **File > Open...** (or press `Ctrl+O`) to browse for a `.tun` file. TunnelCAD also supports importing legacy `.tcm` files via **File > Convert TCM...**, which converts the old format into the current `.tun` format.

### Recent files

The **File > Recent Files** submenu lists previously opened projects for quick access. Click any entry to reopen that project.

## Saving projects

- **File > Save** (`Ctrl+S`) -- saves the current project to its existing file path. If the project has not been saved before, this behaves like Save As.
- **File > Save As...** -- prompts for a new file name and location.

## Modified indicator

When a project has unsaved changes, an asterisk (`*`) appears in the tab caption next to the project name. Closing a modified project (via **File > Close**, `Ctrl+W`, or exiting the application) triggers a save prompt asking whether to save, discard, or cancel.

## Multi-project tabs

Multiple projects can be open simultaneously, each in its own tab. Use **File > Close** (`Ctrl+W`) to close the active project tab, or **File > Close All** to close every open project. Each tab independently tracks its own modified state.

## Activity log / Calendar

Each project carries its own audit log and lightweight task tracker. The Calendar workspace tab records system events (saves, edits, imports, exports, analytics runs) automatically and lets the user add status-tagged notes alongside them. The log is persisted in the `.tun` file. See {doc}`calendar`.

## File format

TunnelCAD projects use the `.tun` extension. The file is XML-based and contains all project data: alignment geometry, line definitions, templates, cross-sections, volume definitions, style libraries, and unit settings. See {doc}`/import-export/file-format` for the full schema reference.

```{toctree}
:maxdepth: 2

tunnel-alignments
forepoling
realignment
sections
settings
units
calendar
```