Hello,

This is my first post on the site and I am not sure my question is posted in the right forum, so I apologize if this is the wrong place. Anyway, this is my very first game and I am doing it in C# and XNA. Currently everything in my tetris game so far is working (left/right movements, dropping down quickly, rotations, etc) and the board is being drawn correctly except when the player fills 10 squares in a row what happens is that the row is just deleted and the rows above it don't fall down. What is confusing is that I am updating the board to shift every row down, but for some reason it is not being updated graphically. Here are the relevant parts of my code.

TetrisBoard class

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Tetris
{
    public class TetrisBoard
    {
        public const int boardCols = 10;
        public const int boardRows = 22;
        public Square[,] board;

        public TetrisBoard()
        {
            board = new Square[boardRows, boardCols];
        }

        public bool isCellFull(int row, int col)
        {
            return board[row, col] != null;
        }

        public void fillCell(int row, int col, Square square)
        {
            board[row, col] = square;
        }

        public void deleteCell(int row, int col)
        {
            board[row, col] = null;
        }

        public void fillTetromino(Tetromino tetromino)
        {
            for (int i = 0; i < tetromino.squares.Length; i++)
            {
                int col = tetromino.squares[i].square.X / Square.width;
                int row = tetromino.squares[i].square.Y / Square.height;
                fillCell(row, col, tetromino.squares[i]);
            }
        }

        public bool canMoveDown(Square square)
        {
            int col = (square.square.X / Square.width);
            int row = (square.square.Y / Square.height) + 1;
            if (row >= boardRows)
                return false;
            return !isCellFull(row, col);
        }

        public bool canMoveDown(Tetromino tetromino)
        {
            for(int i = 0; i < tetromino.squares.Length; i++)
                if(!canMoveDown(tetromino.squares[i]))
                    return false;
            return true;
        }

        public bool canAccelerateDown(Square square)
        {
            int col = (square.square.X / Square.width);
            int row = (square.square.Y / Square.height) + 2;
            if (row >= boardRows)
                return false;
            return !isCellFull(row, col);
        }
        
        public bool canAccelerateDown(Tetromino tetromino)
        {
            for (int i = 0; i < tetromino.squares.Length; i++)
                if (!canAccelerateDown(tetromino.squares[i]))
                    return false;
            return true;
        }

        public bool canMoveLeft(Square square)
        {
            int col = (square.square.X / Square.width) - 1;
            int row = (square.square.Y / Square.height);
            if (col < 0)
                return false;
            return !isCellFull(row , col);
        }

        public bool canMoveLeft(Tetromino tetromino)
        {
            for (int i = 0; i < tetromino.squares.Length; i++)
                if (!canMoveLeft(tetromino.squares[i]))
                    return false;
            return true;
        }

        public bool canMoveRight(Square square)
        {
            int col = (square.square.X / Square.width) + 1;
            int row = (square.square.Y / Square.height);
            if(col >= boardCols)
                return false;
            return !isCellFull(row, col);
        }

        public bool canMoveRight(Tetromino tetromino)
        {
            for (int i = 0; i < tetromino.squares.Length; i++)
                if (!canMoveRight(tetromino.squares[i]))
                    return false;
            return true;
        }

        public bool hasLanded(Tetromino tetromino)
        {
            return !canMoveDown(tetromino);
        }

        public void checkTenInARow()
        {
            for (int i = boardRows - 1; i >= 0; i--)
            {
                bool score = true;
                for (int j = 0; j < boardCols; j++)
                {
                    if (!isCellFull(i, j))
                    {
                        score = false;
                        break;
                    }
                }
                if (score)
                {
                    printBoard();
                    dropDownSquares(i);
                    printBoard();
                }
            }
        }

        public void dropDownSquares(int row)
        {
            for (int i = row; i > 0; i--)
            {
                for (int j = 0; j < boardCols; j++)
                {
                    fillCell(i, j, board[i - 1, j]);
                    deleteCell(i - 1, j);
                }
            }

        }

        public void printBoard()
        {
            for (int i = 0; i < boardRows; i++)
            {
                for (int j = 0; j < boardCols; j++)
                    if (isCellFull(i, j))
                        Console.WriteLine(i + " " + j);
            }
        }
    }
}

And this is part of the Game1.cs class

        protected override void Update(GameTime gameTime)
        {
            // Allows the game to exit
            if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
                this.Exit();

            // TODO: Add your update logic here
            timeSinceLastInput += (float)gameTime.ElapsedGameTime.TotalSeconds;
            if (timeSinceLastInput >= minTimeSinceLastInput)
                keyboardInputHandler();

            timeSinceLastMove += (float)gameTime.ElapsedGameTime.TotalSeconds;
            if (!pause)
            {
                if (timeSinceLastMove >= minTimeSinceLastMove)
                {
                    if (board.canMoveDown(currentPiece))
                    {
                        currentPiece.moveDown();
                        timeSinceLastMove = 0;
                    }
                }
                if (board.hasLanded(currentPiece))
                {
                    board.fillTetromino(currentPiece);
                    board.checkTenInARow();
                    spawnRandomTetromino();
                }
            }
            base.Update(gameTime);
        }


        public void drawTetromino()
        {
            for (int i = 0; i < currentPiece.squares.Length; i++)
                drawSquare(currentPiece.squares[i]);
        }

        public void drawSquare(Square square)
        {
            spriteBatch.Draw(squareTex, square.square, Color.White);
        }

        public void drawBoard()
        {
            for (int i = 0; i < TetrisBoard.boardRows; i++)
            {
                for (int j = 0; j < TetrisBoard.boardCols; j++)
                {
                    if (board.isCellFull(i, j))
                        drawSquare(board.board[i, j]);
                }
            }
        }



        /// <summary>
        /// This is called when the game should draw itself.
        /// </summary>
        /// <param name="gameTime">Provides a snapshot of timing values.</param>
        protected override void Draw(GameTime gameTime)
        {
            GraphicsDevice.Clear(Color.CornflowerBlue);

            // TODO: Add your drawing code here
            spriteBatch.Begin();
            drawBoard();
            drawTetromino();
            spriteBatch.End();
            base.Draw(gameTime);
        }
    }
 

I have been trying to figure out this bug for a while, and I sure could use a new pair of eyes to look at it. I have attached the whole project if you need to see more of the code. Thanks

Well your physics is updating, it's just the visuals that aren't!
Your problem is that when you call the dropDownSquares() function, it sets the deleted square equal to the one above it (which includes its rectangles X and Y values).

Here's a quick fix, you might wanna find a prettier one, given that the rest of your code is nicely organised:

New dropDownSquares:

public void dropDownSquares(int row)
        {
            for (int i = row; i > 0; i--)
            {
                for (int j = 0; j < boardCols; j++)
                {
                  
                    moveCell(i, j, board[i - 1, j]);
                    deleteCell(i - 1, j);
                }
            }
        } 

where the moveCell function is just the fillCell with the changed Y value added:

public void moveCell(int row, int col, Square sq)
        {
            board[row, col] = sq;
            if(sq!=null)board[row, col].square.Y += 16;
        }

Ahhhhhh yes, you are absolutely right. I forgot to update the coordinates, thank you very much :D.

No problem. I agree with Seabolt though- if you're new to debugging code, it's good to get the practice. The more complicated your game gets, the less likely
other people will be able to help!