Lua, what is dt, dy, and dx

number dx
The amount moved along the x-axis since the last time love.mousemoved was called.
number dy
The amount moved along the y-axis since the last time love.mousemoved was called.

dt is the most common shorthand for delta-time, which is usually passed through love.update to represent the amount of time which has passed since it was last called. It is in seconds, but because of the speed of modern processors is usually smaller than 1 values like 0.01 are common.

so the ball will move accordingly every dt

A working D7 to D8 node migration

source:
  plugin: d7_node
  node_type: market_center
  key: d7finra
  constants:
    uid_root: 1
    node_article: 'article'
destination:
  plugin: entity:node
process:
  # Hardcode the destination node type (bundle) as 'migrate_example_beer'.
  id: nid
  type:
    plugin: default_value
    default_value: article
  title: title
  field_mm_mcid: field_mm_mcid
  field_mm_url:
    plugin: iterator
    source: field_mm_url
    process:
      uri: url
      title: title
      options: attributes
  field_core_content_type_tax:
    plugin: sub_process
    source: field_core_content_type_tax

If you can't enable your migrate module due to already active configuration

This was my error message:

complinetmigration already exists in active configuration

This was the solution:

drush sqlq 'SELECT * FROM config WHERE name LIKE "%complinet%";'
drush sqlq 'DELETE FROM config WHERE name LIKE "%complinet%";'
drush sqlq 'DELETE FROM config WHERE name LIKE "%to_D8%";'

also https://www.drupal.org/project/drupal/issues/2877922