How to run a simple agent-based model via abmplot()

New to Julia
1

This simple model in continuous space starts with one dead (immobile) object and 500 live (moving ) ones. If a live object gets close to a dead one, it dies. The result should be a growing pattern. The control panel shows, but the model does not run. Any ideas?

using Agents
using Random

xMax = 100
yMax = 100
extent = (xMax, yMax)
touchDist = 10

println( "Starting here ======================" )

@agent struct Thing( ContinuousAgent{ 2, Float64 } )
    separation::Float64
    alive::Bool
end

rng = Random.MersenneTwister()

function initialize_model(;
    separation = touchDist,
    alive      = true,  )

    space2d = ContinuousSpace( extent; spacing = 1.0, periodic = false )

    model = StandardABM( Thing, space2d; 
                         rng, 
                         agent_step!, 
                         scheduler = Schedulers.Randomly() )
    vel = SVector( -1, -1 ) 
    
    for i = 1:501
        newAgent     = add_agent!( model, vel, touchDist, alive )
        newAgent.pos = SVector( xMax/2, 1 )
    end
    
    model[ 1 ].pos   = SVector( xMax/2, yMax/2 )
    model[ 1 ].alive = false
 
    return model
end

function agent_step!( thing, model )

    if ( !thing.alive ) return 
    end

    nums = rand( rng  ) * 360  
    dx   = cosd( nums )
    dy   = sind( nums )
    newX::Float64 = thing.pos[ 1 ] + dx
    newY::Float64 = thing.pos[ 2 ] + dy

    if ( newX < 1    ) newX = xMax end
    if ( newX > xMax ) newX = 1    end
    if ( newY < 1    ) newY = yMax end
    if ( newY > yMax ) newY = 1    end 

    thing.pos = SVector( newX, newY )

    move_agent!( thing, thing.pos, model )

    nextThing = nearest_neighbor(thing, model::ABM{<:ContinuousSpace}, touchDist ) → nearest
    if( ( nextThing = !isnothing ) && ( !nextThing.alive ) )
        thing.alive = false
    end
end

using GLMakie

model = initialize_model()

plotkwargs = (;
    agent_marker = :circle, 
    agent_color = :red, 
    agent_size = 12
)

fig, ax, abmobs = abmplot( model; add_controls = true, plotkwargs...)
fig