# Basic simulation components

Before you begin defining the simulation content (such as actors, posts, comments, notifications), you may want to change other components of the simulation.

Below are some simulation components that can be changed via the environment variables `.env` file. These include the site name and logo, the number and names of the experimental conditions on your site, and feed order. See the table below for a list and description of these components. 

<table><thead><tr><th width="320">Environment Variable</th><th>Description</th></tr></thead><tbody><tr><td><code>POST_SURVEY</code></td><td><p>(Optional) <em>The URL to the post-study survey</em>. <br>You may want participants to complete a survey when they have completed the study. </p><p><br>If yes, define this variable with your survey link. It is shown when the participant tries to log in to their account after their study is complete. </p><p><img src="https://797468930-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FOR396HK0xjvBHL78w6Qi%2Fuploads%2FG1EazYsGOIXiCEH6LZP5%2Fimage.png?alt=media&#x26;token=eb62d919-5e0c-4551-8bc2-202413a73d42" alt=""><br>If you'd like to integrate this post-study survey with Qualtrics, see <a href="../../../getting-started/launching-your-study#integrating-truman-with-qualtrics">Integrating Qualtrics with Truman</a>. Remember to append <strong>?r_id=</strong> to the end of your survey link and set <code>POST_SURVEY_WITH_QUALTRICS</code> to <code>TRUE</code>.<br><br>If no, remove this variable from the <code>.env</code> file by removing the line from the file.</p></td></tr><tr><td><code>POST_SURVEY_WITH_QUALTRICS</code></td><td><em>TRUE/FALSE</em><br>This label indicates if you would like to integrate a Qualtrics post-study survey with your study. See <a href="../../../getting-started/launching-your-study#integrating-truman-with-qualtrics">Integrating Qualtrics with Truman</a> for more information.</td></tr><tr><td><code>IDENTIFIER</code></td><td><em>Label for participant unique identifier.</em> This label is shown on the form on the <em>Sign Up</em> page. It prompts participants to provide their unique identifier.<br><img src="https://797468930-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FOR396HK0xjvBHL78w6Qi%2Fuploads%2Fa5GP5UAripdATVjhlsIL%2Ftempsnip.png?alt=media&#x26;token=194b8565-5bde-4ed0-8e0a-7d6b5ded202a" alt=""></td></tr><tr><td><code>RESEARCHER_EMAIL</code></td><td><em>The contact email of the researcher.</em> This is shown on the <em>Forgot Your Password</em> page so that participants' may contact you for their password to be reset.<br>See <a href="frequently-asked-questions">FAQs </a>for more information on what to do if a participant has forgotten their password.</td></tr><tr><td><code>NUM_DAYS</code></td><td><p><em>Study duration (a numerical value; in # of days).</em> This indicates how long the simulation should last for participants. So, after the specified number of days has passed since a participant creates their account, their account will be deactivated, and they will not be able to access the site after.</p><p>1 day is 24 hours. </p></td></tr><tr><td><code>SITE_NAME</code></td><td><em>Platform Name.</em> This is shown throughout the platform.</td></tr><tr><td><code>SITE_LOGO</code></td><td><em>File path to the platform logo.</em> This is shown throughout the platform, specifically via the header.</td></tr><tr><td><code>SITE_PICTURE</code></td><td><em>File path to the platform picture.</em> This is shown on the <em>Login</em> and <em>Sign Up.</em><br><img src="https://797468930-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FOR396HK0xjvBHL78w6Qi%2Fuploads%2FqUEJjfRk0fydpYPgogaY%2Ftempsnip.png?alt=media&#x26;token=74d7f255-364f-424f-93eb-73ca45906b71" alt=""></td></tr><tr><td><code>NUM_EXP_CONDITIONS</code></td><td><em>The number of experimental conditions in the experiment.</em> This variable works in conjunction with the variable below. Participants are randomly assigned to an experimental condition upon account creation. This variable defines how many conditions there should be.</td></tr><tr><td><code>EXP_CONDITIONS_NAMES</code></td><td><p><em>The names of the experimental conditions in the experiment.</em> Separate the names with a comma, but no spaces (ex: var1,var2,var3). </p><p>This variable works in conjunction with the variable above. Participants are randomly assigned to an experimental condition upon account creation. This variable defines the labels (names) of these experimental conditions. The names as they appear here are also how they appear in the database.</p></td></tr><tr><td><code>FEED_ORDER</code></td><td><p><em>Indicates how you would like the feed to be shown.</em> Available values include: </p><ul><li>CHRONOLOGICAL: The posts will be shown chronologically on the feed/timeline.</li><li>SHUFFLE: The feed posts will be shuffled on the feed/timeline.</li></ul></td></tr><tr><td><code>CDN</code></td><td><p>(Optional) <em>CDN URL</em>. A content delivery network (CDN) is a network of interconnected servers that caches content near end users. Using a CDN can speed up webpage loading for data-heavy applications.  <br></p><p>In The Truman Platform, a CDN can be used to deliver your actor profile pictures and post pictures.</p><p></p><p>In the default <code>.env</code> file, a CDN URL is provided, but it is for the default simulation. </p><p></p><p>Therefore, <strong>if you change the simulation content</strong> (i.e. define new actors, posts, comments, etc.), <strong>you will need to:</strong> </p><ol><li><strong>Remove this line from the <code>.env</code> file</strong> </li></ol><p>or</p><ol start="2"><li><strong>Change the CDN URL to point to the CDN you are personally using to deliver the static content (pictures).</strong> <br>Note: When setting up your CDN, ensure that the bucket that contains your content has a folder <code>./post_pictures</code> (where all the post pictures are placed in) and a folder <code>./profile_pictures</code> (where all the profile pictures are placed in).</li></ol></td></tr><tr><td><code>REMOVE_FLAGGED_CONTENT</code></td><td><p><em>TRUE/FALSE</em></p><p>When <em>TRUE</em>, flagged content (posts and comments) are entirely from timeline. When <em>FALSE</em>, flagged content appear with an overlay and gives participant the option to unflag the content.</p></td></tr></tbody></table>

### How to change these components

These components can be changed in the `.env` file found in the project folder. It looks like the following when opened with a text file editor:

<figure><img src="https://797468930-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FOR396HK0xjvBHL78w6Qi%2Fuploads%2FLDGo5Bo7N3uTb1NH7jfy%2Fimage.png?alt=media&#x26;token=6f74bb0e-f024-4c2f-b363-e23603e0c5ad" alt=""><figcaption></figcaption></figure>

To change or define a variable, replace the value after the equals sign of the corresponding variable with your desired value.

* For example:
  * If you would like to change the site name to “FootballForums”, then you will need to change the line:&#x20;
    * `SITE_NAME=eatsnap.love` to `SITE_NAME=FootballForums`

{% hint style="info" %}
When changing variable names, there should be no spaces between the variable name, equals sign, and variable value. The following **will not work** because of spacing between the equals sig&#x6E;**.**&#x20;

* <mark style="color:red;">`SITE_NAME= FootballForums`</mark>
* <mark style="color:red;">`SITE_NAME  = FootballForums`</mark>

If your variable *value* has a space, enclose the value with quotes. For example:&#x20;

<mark style="color:green;">`SITE_NAME="Football Forums"`</mark>
{% endhint %}