game folder

code/game/objects/items/tools/weldingtool.dm

@@ -28,6 +28,7 @@
 	var/change_icons = 1
 	var/can_off_process = 0
 	var/light_intensity = 2 //how powerful the emitted light is when used.
+	var/progress_flash_divisor = 10
 	var/burned_fuel_for = 0	//when fuel was last removed
 	heat = 3800
 	tool_behaviour = TOOL_WELDER
@@ -234,6 +235,16 @@
 	if(. && user)
 		user.flash_act(light_intensity)
 
+// Flash the user during welding progress
+/obj/item/weldingtool/tool_check_callback(mob/living/user, amount, datum/callback/extra_checks)
+	. = ..()
+	if(. && user)
+		if (progress_flash_divisor == 0)
+			user.flash_act(min(light_intensity,1))
+			progress_flash_divisor = initial(progress_flash_divisor)
+		else
+			progress_flash_divisor--
+
 // If welding tool ran out of fuel during a construction task, construction fails.
 /obj/item/weldingtool/tool_use_check(mob/living/user, amount)
 	if(!isOn() || !check_fuel())
@@ -358,4 +369,4 @@
 		nextrefueltick = world.time + 10
 		reagents.add_reagent("welding_fuel", 1)
 
-#undef WELDER_FUEL_BURN_INTERVAL
+#undef WELDER_FUEL_BURN_INTERVAL