Put BlockGrid inside of a drawingGroup for better performance. The same method was applied in: WWDC 2019 Session 237 - Building Custom Views with SwiftUI

Changes:

• Adopted the renamed APIs
• Removed AppKit access in the macCatalyst target
• Supported keyboard event handling for macCatalyst
• Some other minor fixes

https://github.com/unixzii/SwiftUI-2048/blob/34f315a4103527eac366403b9e4632326cc2f257/SwiftUI2048/Models/GameLogic.swift#L131

This function can be optimized like this so that it can create any nums of blocks.

@discardableResult fileprivate func generateNewBlock() -> Bool {
      var blankLocations = [BlockMatrixType.Index]()
      for rowIndex in 0..<4 {
          for colIndex in 0..<4 {
              let index = (colIndex, rowIndex)
              if _blockMatrix[index] == nil {
                  blankLocations.append(index)
              }
          }
      }
      
      guard blankLocations.count >= 1 else {
          return false
      }
      
      // Don't forget to sync data.
      defer {
          objectWillChange.send(self)
      }
      
      _blockMatrix.place(IdentifiedBlock(id: newGlobalID, number: 2), to: blankLocations.randomElement()!)
      
      return true
  }
  
  @discardableResult fileprivate func generateNewBlocks(_ num: Int = 1) -> Bool {
      guard num > 0 else {
          return false
      }
      
      for _ in 0..<num {
          if !generateNewBlock() {
              return false
          }
      }
      
      return true
  }

https://github.com/unixzii/SwiftUI-2048/blob/34f315a4103527eac366403b9e4632326cc2f257/SwiftUI2048/Models/GameLogic.swift#L74

fixed:

if let block = _blockMatrix[axis ? (col, row) : (row, col)] {
    rowSnapshot.append(block)
    compactRow.append(block)
} else { // add else here
    rowSnapshot.append(nil)
}