Fulgora's Vault ruins show occasional remnants of activity...
Ancient defense drones are still active!

Kickstart your base with the sparse scrap deposits,
then find ways to deal with the aggressive drones that keep emerging from the vault ruins on the srcap-rich island.
Their attacks will only disable your mining drills, never destroy them and the rest of your base is completely safe.

This is not meant to be a constant threat like biters, instead meant as a fun puzzle to give live to an otherwise dead planet.

Video: https://www.youtube.com/watch?v=-ZuOM_GK9Ys

Features

• Drones will actually appear to rise out of the vertical shaft of the now indestructible vault ruins
• Drones will only patrol a certain radius around the vault
• Drones will die over time just like personal combat robots, so at minimum you will need to automate repairs
• Unique system where enemy drone attacks will not destroy buildings, but disable them at 1 HP instead
  Your roboports, trains and inserters are safe however!
• You can also attempt to defeat the waves using turrets, be creative!
• Attack wave size and frequency are scaled to mining speed (currently depends on scrap depletion)
• Evolution system, total mined scrap will increase wave size
• Custom target selection / random movement
• Tweaks to drone HP, resistances to balance for turret vs drone combat
• Can be added into a running game, but you'll likely have destroyed the vault ruins already, but they could be spawned in with the editor

Potential features / TODO

• The drone targeting/movement code should be rewritten for better performance
• Allow disabling alerts of damaged or destroyed entities near vault ruins
• Add a way of player combat robots to be deployed in response, for sweet bot on bot action
• Consider other behaviors for the enemy drones, like an optional mode where they actually assault or mess with your base

• Ideas for a reward have been suggested, like "digging deeper" over time causes stronger drones to spawn (quality?), but in turn scrap will also have quality.

• To avoid construction bots being shot at, I disable the chest of repair packs via circuits and a mod I made to detect enemy drones:
  https://mods.factorio.com/mod/hexcoder-scanner-combinator
  Since this is brittle the there could be other ways to fix this directly in the mod

This mod is somewhat experimental, All feedback is welcome!