Add basic score calculation

Tetris/ContentView.swift

@@ -34,6 +34,8 @@ struct ContentView: View {
                         } else {
                             Rectangle().foregroundColor(.clear).frame(width: 50, height: 50)
                         }
+                        Text("Score")
+                        Text(verbatim: self.controller.score.description)
                     }
                         .padding(.leading, 8)
                     BoardView(board: self.$controller.board, currentPiece: self.$controller.currentPiece, droppedPiece: self.$controller.currentPieceAtDropPoint)

TetrisKit/GameController.swift

@@ -26,6 +26,9 @@ public class GameController: ObservableObject {
     @Published public var currentPieceAtDropPoint: GamePiece?
     @Published public var nextTetrominoes: [Tetromino] = [.random(), .random(), .random()]
     @Published public var heldTetromino: Tetromino?
+    
+    @Published public var score = 0
+    var previousPieceWasTetris = false
 
     public var ended: Bool {
         return (0..<width).first(where: { board[$0, 0] }) != nil
@@ -56,16 +59,29 @@ public class GameController: ObservableObject {
     }
     
     func clearLines() {
+        var cleared = 0
         var row = height - 1
         while row >= 0 {
             if board.rowFull(row) {
                 board.tiles.remove(at: row)
+                cleared += 1
             }
             row -= 1
         }
-        for _ in 0..<height - board.tiles.count {
+        for _ in 0..<cleared {
             board.tiles.insert(Array(repeating: nil, count: width), at: 0)
         }
+        
+        if cleared == 4 {
+            score += previousPieceWasTetris ? 1200 : 800
+            previousPieceWasTetris = true
+        } else if cleared == 3 {
+            score += 500
+        } else if cleared == 2 {
+            score += 300
+        } else if cleared == 1 {
+            score += 100
+        }
     }
     
     public func step() {