explicit recipe unlocking

bin/test/data/config/recipes.toml

@@ -40,6 +40,38 @@ inputs = [{item = "iron_ingot", amount = 4}]
 outputs = [{item = "building_block", amount = 10}]
 duration_seconds = 4.0
 
+[[recipe]]
+id = "premium_circuit"
+building = "assembler"
+unlock_at_station_level = -1
+inputs = [{item = "circuit_board", amount = 1}]
+outputs = [{item = "premium_circuit", amount = 1}]
+duration_seconds = 8.0
+
+[[recipe]]
+id = "quick_circuit"
+building = "assembler"
+unlock_at_station_level = 0
+inputs = [{item = "copper_ingot", amount = 3}]
+outputs = [{item = "circuit_board", amount = 1}]
+duration_seconds = 3.0
+
+[[recipe]]
+id = "advanced_circuit"
+building = "assembler"
+unlock_at_station_level = 1
+inputs = [{item = "iron_ingot", amount = 5}]
+outputs = [{item = "circuit_board", amount = 1}]
+duration_seconds = 6.0
+
+[[recipe]]
+id = "exotic_alloy"
+building = "assembler"
+unlock_at_station_level = 0
+inputs = [{item = "exotic_ore", amount = 2}]
+outputs = [{item = "exotic_alloy", amount = 1}]
+duration_seconds = 10.0
+
 [[recipe]]
 id = "reprocessing_cycle"
 building = "reprocessing_plant"