Display forward slash when research is already blocked by another research

src/main/kotlin/ru/dbotthepony/mc/otm/android/AndroidResearch.kt

@@ -69,14 +69,26 @@ abstract class AndroidResearch(val type: AndroidResearchType<*>, val capability:
 			return false
 		}
 
-		for (research in prerequisites) {
-			if (!capability.getResearch(research).isResearched) {
-				return false
+		if (!allPrerequisitesResearched || anyBlockerResearched) {
+			return false
+		}
+
+		return true
+	}
+
+	val anyBlockerResearched: Boolean get() {
+		for (research in blockedBy) {
+			if (capability.getResearch(research).isResearched) {
+				return true
 			}
 		}
 
-		for (research in blockedBy) {
-			if (capability.getResearch(research).isResearched) {
+		return false
+	}
+
+	val allPrerequisitesResearched: Boolean get() {
+		for (research in prerequisites) {
+			if (!capability.getResearch(research).isResearched) {
 				return false
 			}
 		}

src/main/kotlin/ru/dbotthepony/mc/otm/client/render/Widgets18.kt

@@ -12,4 +12,5 @@ object Widgets18 {
 	val COLON = GRID.next()
 	val C = GRID.next()
 	val CROSS = GRID.next()
+	val FORWARD_SLASH = GRID.next()
 }

src/main/kotlin/ru/dbotthepony/mc/otm/client/screen/AndroidStationScreen.kt

@@ -77,7 +77,7 @@ private fun isTree(root: AndroidResearchType<*>): Boolean {
 	return true
 }
 
-typealias LinePos = Pair<Pair<Float, Float>, Pair<Float, Float>>
+private typealias LinePos = Pair<Pair<Float, Float>, Pair<Float, Float>>
 
 private class Tree(val node: AndroidResearchType<*>) : Iterable<Tree> {
 	val subtrees = ArrayList<Tree>()
@@ -309,6 +309,10 @@ private open class AndroidResearchButton(
 			RGBAColor.RED.setSystemColor()
 
 			Widgets18.CROSS.render(stack)
+		} else if (node.anyBlockerResearched) {
+			RGBAColor.RED.setSystemColor()
+
+			Widgets18.FORWARD_SLASH.render(stack)
 		}
 
 		val text = node.iconText