plans: [
  {
    unit: dagger
    time: 1200
    requirements: [
      lead/40
      graphite/15
    ]
  }
  {
    unit: crawler
    time: 600
    requirements: [
      coal/10
      graphite/10
    ]
  }
  {
    unit: nova
    time: 1800
    requirements: [
      copper/15
      lead/60
      silicon/15
    ]
  }
]
requirements: [
  copper/50
  lead/100
  graphite/50
]