diff --git a/src/docs/part1/simple_detector.md b/src/docs/part1/simple_detector.md
index b8f8e34af1370f52825aae0468094b11f11bb45d..afb409b5d358714f6a3f9b3d2e6ba96e6d41ebab 100644
--- a/src/docs/part1/simple_detector.md
+++ b/src/docs/part1/simple_detector.md
@@ -4,40 +4,55 @@ title: "Simple Detector"
 
 ## Setup 
 
+Note all these commands assume you are in an `eic-shell` singularity session.
+
 ```bash
 git clone https://eicweb.phy.anl.gov/EIC/tutorials/ip6_tutorial_1.git part1
 cd part1
 ```
 
-You will find the following files and directories.
-```shell
-.
-├── elements.xml
-├── gem_tracker.xml
-├── gps.mac
-├── materials.xml
-├── README.md
-├── rootlogon.C
-├── run_example
-└── scripts
-    ├── example_Acts.cxx
-    ├── example_cell_size.cxx
-    ├── example_digi.cxx
-    ├── example_hit_recon.cxx
-    ├── example_seg_size.cxx
-    ├── example_tracking.cxx
-    └── mag_field.cxx
-```
+## Inspect files 
 
+Look around see what's what.
 The files 
-[`materials.xml`](https://eicweb.phy.anl.gov/EIC/tutorials/ip6_tutorial_1/blob/master/materials.xml), 
-[`elements.xml`](https://eicweb.phy.anl.gov/EIC/tutorials/ip6_tutorial_1/blob/master/elements.xml),
+[`compact/materials.xml`](https://eicweb.phy.anl.gov/EIC/tutorials/ip6_tutorial_1/blob/master/compact/materials.xml), 
+[`compact/elements.xml`](https://eicweb.phy.anl.gov/EIC/tutorials/ip6_tutorial_1/blob/master/compact/elements.xml),
 and 
 [`gem_tracker.xml`](https://eicweb.phy.anl.gov/EIC/tutorials/ip6_tutorial_1/blob/master/gem_tracker.xml) 
 are the compact detector description files. The first two files are included in 
-the main `gem_tracker.xml` file. Note these files are conventionally found in 
-directories named compact.
+the main `gem_tracker.xml` file. Note these files are often found in 
+directories named compact (but not always).
+
+## Compile the detector library
+
+```
+mkdir build
+cmake ../. -DCMAKE_INSTALL_PREFIX=../../local 
+make -j4 install
+```
 
+## Look at geometry
+
+
+```
+dd_web_display --export gem_tracker.xml
+```
+Copy the generated file `detector_geometry.root` to your local machine.
+Then open the [web viewer](https://eic.phy.anl.gov/geoviewer/), click on the `...` and open the local root file.
+
+
+```xml
+    <detector id="2" name="GEMTracker" vis="RedVis" type="my_GEMTracker" readout="GEMTrackerHits" > 
+      <layer id="1" z="-100 *cm" inner_r="40*cm"  outer_r="120*cm"   phi0_offset="0.0*deg" />
+      <layer id="2" z="-80 *cm"  inner_r="30*cm"  outer_r="90*cm"    phi0_offset="0.0*deg" />
+      <layer id="3" z="-60 *cm"  inner_r="20*cm"  outer_r="70*cm"    phi0_offset="0.0*deg" />
+      <layer id="4" z="-40 *cm"  inner_r="20*cm"  outer_r="50.0*cm"  phi0_offset="0.0*deg" />
+      <layer id="5" z=" 40 *cm"  inner_r="20*cm"  outer_r="50.0*cm" phi0_offset="0.0*deg" />
+      <layer id="6" z=" 60 *cm"  inner_r="25*cm"  outer_r="70.0*cm" phi0_offset="0.0*deg" />
+      <layer id="7" z=" 80 *cm"  inner_r="30*cm"  outer_r="90.0*cm" phi0_offset="0.0*deg" />
+      <layer id="8" z="100 *cm"  inner_r="40*cm"  outer_r="100.0*cm" phi0_offset="0.0*deg" />
+    </detector>
+```
 
 
 
@@ -50,7 +65,6 @@ ddsim  --runType run  --enableG4GPS \
    --outputFile gem_tracker_sim.root 
 ```
 
-
 This will run geant4 using the General Particle Source (GPS) tool.
 The output will be a root file containing the generated events and GEM tracker hits.