modified: src/@rocketseat/gatsby-theme-docs/styles/global.js

	modified:   src/@rocketseat/gatsby-theme-docs/styles/theme.js
	modified:   src/docs/part3/simulating_detectors.md

src/@rocketseat/gatsby-theme-docs/styles/global.js

@@ -33,7 +33,7 @@ export default function GlobalStyle() {
 
         h1 {
           font-size: 32px;
-          color: #333;
+          color: #262626;
           font-weight: normal;
           margin-bottom: 24px;
         }
@@ -63,7 +63,7 @@ export default function GlobalStyle() {
         }
 
         p {
-          color: #737380;
+          color: #262626;
           font-size: 16px;
           line-height: 28px;
           margin-bottom: 16px;
@@ -134,7 +134,7 @@ export default function GlobalStyle() {
 
         ul,
         ol {
-          color: #737380;
+          color: #262626;
           padding-left: 15px;
           margin-bottom: 16px;
 

src/@rocketseat/gatsby-theme-docs/styles/theme.js

@@ -4,7 +4,7 @@ export default {
     background: '#fff',
     sidebar: {
       background: '#ffffff',
-      link: '#999',
+      link: '#737373',
       heading: '#aaa',
       linkActive: '#13131A',
       itemActive: '#F5F5FA',

src/docs/part3/simulating_detectors.md

@@ -2,5 +2,37 @@
 title: 'Tutorial Part 3: Running the Simulation'
 ---
 
+## Background
+
+This tutorial assumes some familiarity with Geant4. Please refer to the [Geant4 
+Application Developers 
+Guide](http://geant4-userdoc.web.cern.ch/geant4-userdoc/UsersGuides/ForApplicationDeveloper/html/index.html)
+for a refresher or one of the many useful [Geant4 tutorial 
+events](http://geant4.web.cern.ch/past-events).
+
+## Running the Geant4 Simulation
+
+DDG4 is the Geant4 wrapping part of the DD4hep libraries.
+There are a few ways to setup and run the Geant4 simulation, each with their own 
+benefits.
+
+1. `ddsim` - a robust python program that is highly configurable. Good for 
+   running quick simulations using built-in detector constructions, built-in 
+   hit data model, and built-in sensitive detectors (tracker or calorimeter).  
+   We used `ddsim` in [part 1](part1/simple_detector) of this tutorial. See 
+   `ddsim -h` for more details.
+2. Manual configuring the DDG4 setup. This can be achieved using XML, C++ (eg 
+   in a ROOT script), or using the python interface. As we will see, this 
+   allows for a high degree of customization and control over how gean4 used 
+   and the output generated.
+
+This part of the tutorial will use the python interface but converting to C++ 
+or XML should be straightforward.
+
+
+## 
+
+
+
 To be completed.