Question: First, I'm very new in ReactJS. I've done simple reactjs project based on following link. <http://www.tutorialspoint.com/reactjs/reactjs_environment_setup.htm> and I can run and test perfectly by running "`npm start`". But when I'm trying to integrate with expressJs as edit/developed as follow coding, I cannot render at all.

Package.json

```
  "scripts": {
    "start": "node server.js"
  }

```

server.js

```
var express = require('express');
var path = require('path');

var app = express();

var isProduction = process.env.NODE_ENV === 'production';
var port = isProduction ? process.env.PORT : 3000;
var publicPath = path.resolve(__dirname, '/');

// We point to our static assets
app.use(express.static(publicPath));
console.log(publicPath)

// And run the server
app.listen(port, function () {
  console.log('Server running on port ' + port);
});

```

Whenever I render as "`npm start`", encounter as follow.

> 
> Cannot GET /
> 
> 
>

Answer: 
Another simple mistake for new Unity users. Spelling counts! Simply replace `onCollisionEnter` with `OnCollisionEnter`. The callback functions are case sensitive and their first letter is usually **capitalized**. 

If changing this does not work, attach Rigidbody to your enemy too. Make sure they both have Colliders attached to both of them and that **IsTrigger** is not `enabled`.
Several solutions could fit. Maybe you simply forgot to set the tag on your enemy?
Please have a look at the Unity3D collision matrix (<https://docs.unity3d.com/Manual/CollidersOverview.html> - at the bottom of the page). 

The collision matrix tells you when you will get collision messages. E.g. you can't have a static collider colliding with a rigidbody collider. Recheck all your gameobjects. Are they fitting the needs of a collision?