Added Triremes and water combat!

Credits.md

@@ -17,6 +17,7 @@ All the following are from [the Noun Project](https://thenounproject.com) licenc
 * [Bow And Arrow](https://thenounproject.com/search/?q=Bow%20and%20Arrow&i=338261) By Viktor Ostrovsky for Archer
 * [Bow](https://thenounproject.com/search/?q=bow&i=101736) By Arthur Shlain for Bowman
 * [Fishing Vessel](https://thenounproject.com/term/fishing-vessel/23815/) By Luis Prado for Work Boats
+* [Greek Trireme](https://thenounproject.com/search/?q=ancient%20boat&i=1626303) By Zachary McCune for Trireme
 * [Chariot](https://thenounproject.com/search/?q=Chariot&i=1189930) By Andrew Doane for Chariot Archer
 * [Spear](https://thenounproject.com/search/?q=Spear&i=11432) By Stephen Copinger for Spearman
 

android/assets/jsons/Units.json

@@ -70,6 +70,17 @@
 		movement:4,
 		cost: 30,
 		requiredTech:"Sailing",
+		uniques:["Cannot enter ocean tiles until Astronomy"]
+		hurryCostModifier:20
+	},
+	{
+		name:"Trireme",
+		unitType:"WaterMelee",
+		movement:4,
+		strength:10,
+		cost: 45,
+		requiredTech:"Sailing",
+		uniques:["Cannot enter ocean tiles"]
 		hurryCostModifier:20
 	},
 	{

core/src/com/unciv/logic/map/MapUnit.kt

@@ -8,7 +8,6 @@ import com.unciv.logic.civilization.CivilizationInfo
 import com.unciv.models.gamebasics.GameBasics
 import com.unciv.models.gamebasics.tile.TerrainType
 import com.unciv.models.gamebasics.unit.BaseUnit
-import com.unciv.models.gamebasics.unit.UnitType
 import com.unciv.ui.utils.getRandom
 import java.text.DecimalFormat
 import java.util.*
@@ -98,17 +97,26 @@ class MapUnit {
         return "$name - $owner"
     }
 
-    /**
-     * Designates whether we can walk to the tile - without attacking
-     */
-    fun canMoveTo(tile: TileInfo): Boolean {
+    fun canPassThrough(tile: TileInfo):Boolean{
         val tileOwner = tile.getOwner()
         if(tile.getBaseTerrain().type==TerrainType.Water && baseUnit.unitType.isLandUnit())
             return false
         if(tile.getBaseTerrain().type==TerrainType.Land && baseUnit.unitType.isWaterUnit())
             return false
+        if(tile.baseTerrain=="Ocean" && baseUnit.uniques.contains("Cannot enter ocean tiles until Astronomy")
+                && !civInfo.tech.isResearched("Astronomy"))
+            return false
+        if(tile.baseTerrain=="Ocean" && baseUnit.uniques.contains("Cannot enter ocean tiles")) return false
         if(tileOwner!=null && tileOwner.civName!=owner
                 && (tile.isCityCenter() || !civInfo.canEnterTiles(tileOwner))) return false
+        return true
+    }
+
+    /**
+     * Designates whether we can walk to the tile - without attacking
+     */
+    fun canMoveTo(tile: TileInfo): Boolean {
+        if(!canPassThrough(tile)) return false
 
         if (baseUnit().unitType.isCivilian())
             return tile.civilianUnit==null && (tile.militaryUnit==null || tile.militaryUnit!!.owner==owner)

core/src/com/unciv/logic/map/UnitMovementAlgorithms.kt

@@ -1,7 +1,6 @@
 package com.unciv.logic.map
 
 import com.badlogic.gdx.math.Vector2
-import com.unciv.models.gamebasics.tile.TerrainType
 
 class UnitMovementAlgorithms(val unit:MapUnit) {
     val tileMap = unit.getTile().tileMap
@@ -24,6 +23,7 @@ class UnitMovementAlgorithms(val unit:MapUnit) {
         return to.lastTerrain.movementCost.toFloat() // no road
     }
 
+
     fun getDistanceToTilesWithinTurn(origin: Vector2, unitMovement: Float): HashMap<TileInfo, Float> {
         if(unitMovement==0f) return hashMapOf()
         val distanceToTiles = LinkedHashMap<TileInfo, Float>()
@@ -36,13 +36,7 @@ class UnitMovementAlgorithms(val unit:MapUnit) {
             for (tileToCheck in tilesToCheck)
                 for (neighbor in tileToCheck.neighbors) {
                     var totalDistanceToTile:Float
-                    val neighborOwner = neighbor.getOwner()
-                    val isOwnedByEnemy = neighborOwner!=null && neighborOwner!=unit.civInfo
-                    if ( (unit.baseUnit.unitType.isLandUnit() && neighbor.getBaseTerrain().type== TerrainType.Water)
-                            || (isOwnedByEnemy && neighbor.isCityCenter())// Enemy city,
-                            || (neighbor.getUnits().isNotEmpty() && neighbor.getUnits().first().civInfo!=unit.civInfo) // Enemy unit
-                            || (isOwnedByEnemy && !unit.civInfo.canEnterTiles(neighborOwner!!)) // enemyTile
-                    )
+                    if (!unit.canPassThrough(neighbor))
                         totalDistanceToTile = unitMovement // Can't go here.
                     // The reason that we don't just "return" is so that when calculating how to reach an enemy,
                     // You need to assume his tile is reachable, otherwise all movement algs on reaching enemy

core/src/com/unciv/models/gamebasics/unit/BaseUnit.kt

@@ -24,7 +24,7 @@ class BaseUnit : INamed, IConstruction, ICivilopedia {
     internal var unbuildable: Boolean = false // for special units like great people
     var requiredTech:String? = null
     var requiredResource:String? = null
-    var uniques:HashSet<String>?=null
+    var uniques =HashSet<String>()
     var obsoleteTech:String?=null
     var upgradesTo:String? = null
     var replaces:String?=null

core/src/com/unciv/models/gamebasics/unit/UnitType.kt

@@ -8,6 +8,7 @@ enum class UnitType{
     Scout,
     Mounted,
     WaterCivilian,
+    WaterMelee,
     Siege;
 
     fun isMelee(): Boolean {