Package-level declarations

In 1.13+ crystals need one block air above to be placed.

In 1.12.2 crystals need two blocks air above to be placed.

Positions are only considered if they're obsidian or bedrock because that are the only blocks you can place crystals on.

Depending on the settings, we only take upper block sides but is the checked side in range (and visible)?

Uses the prediction to check if the future crystal will be blocked by players in the next ticks.

Crystals only deal damage if they are placed below the target, because obsidian or bedrock base blocks will block the explosion otherwise.