Spread the Infection

The infection is spread by Devils contacting each other, so we will set it up so that if a red and a black Devil collide, the black one will change colour to red.

Go to the Collisions workspace.  Look in My Blocks>Devils for the Collision block and drag it out. Set up the collision as below.  Hint:  You can use Ctrl-C and Ctrl-V to copy and paste blocks.

Both sections of the Collisions block are set up to be identical, as it does not matter which Devil in the collision is red, they both should become red afterwards.

Go to SpaceLand and test to make sure the collisions work as expected.

Monitor the Infection

We will set up monitors to keep count of the healthy and infected Devils.

Goto the Runtime area and drag in a Monitor block (from Setup and Run)

Now add a count everyone with block.  Then add Color = black

Copy and paste the block.  Change it to be Color = red. 

Rename one monitor Healthy and the other Infected.

Devils Weaken and Die

Sick Devils get weaker over time.  We will use a variable to store the energy level for each Devil.  For sick Devils, we will repeatedly reduce this value by a small random amount.  When it reaches zero, the Devil will die.

	In the Devils workspace, drag in an agent number block, and name it energy.  This is our energy variable.
	Switch to the Setup workspace, and under My Blocks>Devils, drag the set energy block into the Create Devils action. Set the level to be 200.

 Go back to the Devils workspace, and we will create a Procedure for Devils getting weaker, as below.

Finally switch back to the Runtime workspace, and from My Blocks, drag a Get Weaker block into the Forever loop.