add calc

.gitignore

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+.DS_Store
+/dist/
+node_modules/
+yarn-error.log

README.md

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+# Scratchpad
+
+This is an [Observable Framework](https://observablehq.com/framework) project. To start the local preview server, run:
+
+```
+npm run dev
+```
+
+Then visit <http://localhost:3000> to preview your project.
+
+For more, see <https://observablehq.com/framework/getting-started>.
+
+## Project structure
+
+A typical Framework project looks like this:
+
+```ini
+.
+├─ src
+│  ├─ components
+│  │  └─ timeline.js           # an importable module
+│  ├─ data
+│  │  ├─ launches.csv.js       # a data loader
+│  │  └─ events.json           # a static data file
+│  ├─ example-dashboard.md     # a page
+│  ├─ example-report.md        # another page
+│  └─ index.md                 # the home page
+├─ .gitignore
+├─ observablehq.config.js      # the project config file
+├─ package.json
+└─ README.md
+```
+
+**`src`** - This is the “source root” — where your source files live. Pages go here. Each page is a Markdown file. Observable Framework uses [file-based routing](https://observablehq.com/framework/routing), which means that the name of the file controls where the page is served. You can create as many pages as you like. Use folders to organize your pages.
+
+**`src/index.md`** - This is the home page for your site. You can have as many additional pages as you’d like, but you should always have a home page, too.
+
+**`src/data`** - You can put [data loaders](https://observablehq.com/framework/loaders) or static data files anywhere in your source root, but we recommend putting them here.
+
+**`src/components`** - You can put shared [JavaScript modules](https://observablehq.com/framework/javascript/imports) anywhere in your source root, but we recommend putting them here. This helps you pull code out of Markdown files and into JavaScript modules, making it easier to reuse code across pages, write tests and run linters, and even share code with vanilla web applications.
+
+**`observablehq.config.js`** - This is the [project configuration](https://observablehq.com/framework/config) file, such as the pages and sections in the sidebar navigation, and the project’s title.
+
+## Command reference
+
+| Command           | Description                                              |
+| ----------------- | -------------------------------------------------------- |
+| `npm install`            | Install or reinstall dependencies                        |
+| `npm run dev`        | Start local preview server                               |
+| `npm run build`      | Build your static site, generating `./dist`              |
+| `npm run deploy`     | Deploy your project to Observable                        |
+| `npm run clean`      | Clear the local data loader cache                        |
+| `npm run observable` | Run commands like `observable help`                      |

observablehq.config.js

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+// See https://observablehq.com/framework/config for documentation.
+export default {
+  // The project’s title; used in the sidebar and webpage titles.
+  title: "Scratchpad",
+
+  // The pages and sections in the sidebar. If you don’t specify this option,
+  // all pages will be listed in alphabetical order. Listing pages explicitly
+  // lets you organize them into sections and have unlisted pages.
+  // pages: [
+  //   {
+  //     name: "Examples",
+  //     pages: [
+  //       {name: "Dashboard", path: "/example-dashboard"},
+  //       {name: "Report", path: "/example-report"}
+  //     ]
+  //   }
+  // ],
+
+  // Content to add to the head of the page, e.g. for a favicon:
+  head: '<link rel="icon" href="observable.png" type="image/png" sizes="32x32">',
+
+  // The path to the source root.
+  root: "src",
+
+  // Some additional configuration options and their defaults:
+  // theme: "default", // try "light", "dark", "slate", etc.
+  // header: "", // what to show in the header (HTML)
+  // footer: "Built with Observable.", // what to show in the footer (HTML)
+  // sidebar: true, // whether to show the sidebar
+  // toc: true, // whether to show the table of contents
+  // pager: true, // whether to show previous & next links in the footer
+  // output: "dist", // path to the output root for build
+  // search: true, // activate search
+  // linkify: true, // convert URLs in Markdown to links
+  // typographer: false, // smart quotes and other typographic improvements
+  // cleanUrls: true, // drop .html from URLs
+};