The Tetris game in IronPython Mono Winforms

The tetris game is one of the most popular computer games ever created. The original game was designed and programmed by a Russian programmer Alexey Pajitnov in 1985. Since then, Tetris is available on almost every computer platform in lots of variations. Even my mobile phone has a modified version of the tetris game.

Tetris is called a falling block puzzle game. In this game, we have seven different shapes called tetrominoes. S-shape, Z-shape, T-shape, L-shape, Line-shape, MirroredL-shape and a Square-shape. Each of these shapes is formed with four squares. The shapes are falling down the board. The object of the tetris game is to move and rotate the shapes, so that they fit as much as possible. If we manage to form a row, the row is destroyed and we score. We play the tetris game until we top out.

The development

We do not have images for our tetris game, we draw the tetrominoes using the drawing API available in the Winforms library. Behind every computer game, there is a mathematical model. So it is in tetris.

Some ideas behind the game.

• We use `Timer` to create a game cycle
• The tetrominoes are drawn
• The shapes move on a square by square basis (not pixel by pixel)
• Mathematically a board is a simple list of numbers

The following example is a modified version of the Tetris game, available with PyQt4 installation files.

tetris.py
```#!/usr/bin/ipy

import clr

from System.Windows.Forms import Application, Form, FormBorderStyle
from System.Windows.Forms import UserControl, Keys, Timer, StatusBar
from System.Drawing import Size, Color, SolidBrush, Pen
from System.Drawing.Drawing2D import LineCap
from System.ComponentModel import Container
from System import Random

class Tetrominoes(object):
NoShape = 0
ZShape = 1
SShape = 2
LineShape = 3
TShape = 4
SquareShape = 5
LShape = 6
MirroredLShape = 7

class Board(UserControl):
BoardWidth = 10
BoardHeight = 22
Speed = 200
ID_TIMER = 1

def __init__(self):
self.Text = 'Snake'

self.components = Container()
self.isWaitingAfterLine = False
self.curPiece = Shape()
self.nextPiece = Shape()
self.curX = 0
self.curY = 0
self.numLinesRemoved = 0
self.board = []

self.DoubleBuffered = True

self.isStarted = False
self.isPaused = False

self.timer = Timer(self.components)
self.timer.Enabled = True
self.timer.Interval = Board.Speed
self.timer.Tick += self.OnTick

self.Paint += self.OnPaint
self.KeyUp += self.OnKeyUp

self.ClearBoard()

def ShapeAt(self, x, y):
return self.board[(y * Board.BoardWidth) + x]

def SetShapeAt(self, x, y, shape):
self.board[(y * Board.BoardWidth) + x] = shape

def SquareWidth(self):
return self.ClientSize.Width / Board.BoardWidth

def SquareHeight(self):
return self.ClientSize.Height / Board.BoardHeight

def Start(self):
if self.isPaused:
return

self.isStarted = True
self.isWaitingAfterLine = False
self.numLinesRemoved = 0
self.ClearBoard()

self.NewPiece()

def Pause(self):
if not self.isStarted:
return

self.isPaused = not self.isPaused
statusbar = self.Parent.statusbar

if self.isPaused:
self.timer.Stop()
statusbar.Text = 'paused'
else:
self.timer.Start()
statusbar.Text = str(self.numLinesRemoved)

self.Refresh()

def ClearBoard(self):
for i in range(Board.BoardHeight * Board.BoardWidth):
self.board.append(Tetrominoes.NoShape)

def OnPaint(self, event):

g = event.Graphics

size = self.ClientSize
boardTop = size.Height - Board.BoardHeight * self.SquareHeight()

for i in range(Board.BoardHeight):
for j in range(Board.BoardWidth):
shape = self.ShapeAt(j, Board.BoardHeight - i - 1)
if shape != Tetrominoes.NoShape:
self.DrawSquare(g,
0 + j * self.SquareWidth(),
boardTop + i * self.SquareHeight(), shape)

if self.curPiece.GetShape() != Tetrominoes.NoShape:
for i in range(4):
x = self.curX + self.curPiece.x(i)
y = self.curY - self.curPiece.y(i)
self.DrawSquare(g, 0 + x * self.SquareWidth(),
boardTop + (Board.BoardHeight - y - 1) * self.SquareHeight(),
self.curPiece.GetShape())

g.Dispose()

def OnKeyUp(self, event):

if not self.isStarted or self.curPiece.GetShape() == Tetrominoes.NoShape:
return

key = event.KeyCode

if key == Keys.P:
self.Pause()
return

if self.isPaused:
return
elif key == Keys.Left:
self.TryMove(self.curPiece, self.curX - 1, self.curY)
elif key == Keys.Right:
self.TryMove(self.curPiece, self.curX + 1, self.curY)
elif key == Keys.Down:
self.TryMove(self.curPiece.RotatedRight(), self.curX, self.curY)
elif key == Keys.Up:
self.TryMove(self.curPiece.RotatedLeft(), self.curX, self.curY)
elif key == Keys.Space:
self.DropDown()
elif key == Keys.D:
self.OneLineDown()

def OnTick(self, sender, event):

if self.isWaitingAfterLine:
self.isWaitingAfterLine = False
self.NewPiece()
else:
self.OneLineDown()

def DropDown(self):
newY = self.curY
while newY > 0:
if not self.TryMove(self.curPiece, self.curX, newY - 1):
break
newY -= 1

self.PieceDropped()

def OneLineDown(self):
if not self.TryMove(self.curPiece, self.curX, self.curY - 1):
self.PieceDropped()

def PieceDropped(self):
for i in range(4):
x = self.curX + self.curPiece.x(i)
y = self.curY - self.curPiece.y(i)
self.SetShapeAt(x, y, self.curPiece.GetShape())

self.RemoveFullLines()

if not self.isWaitingAfterLine:
self.NewPiece()

def RemoveFullLines(self):
numFullLines = 0

statusbar = self.Parent.statusbar

rowsToRemove = []

for i in range(Board.BoardHeight):
n = 0
for j in range(Board.BoardWidth):
if not self.ShapeAt(j, i) == Tetrominoes.NoShape:
n = n + 1

if n == 10:
rowsToRemove.append(i)

rowsToRemove.reverse()

for m in rowsToRemove:
for k in range(m, Board.BoardHeight):
for l in range(Board.BoardWidth):
self.SetShapeAt(l, k, self.ShapeAt(l, k + 1))

numFullLines = numFullLines + len(rowsToRemove)

if numFullLines > 0:
self.numLinesRemoved = self.numLinesRemoved + numFullLines
statusbar.Text = str(self.numLinesRemoved)
self.isWaitingAfterLine = True
self.curPiece.SetShape(Tetrominoes.NoShape)
self.Refresh()

def NewPiece(self):
self.curPiece = self.nextPiece
statusbar = self.Parent.statusbar
self.nextPiece.SetRandomShape()
self.curX = Board.BoardWidth / 2 + 1
self.curY = Board.BoardHeight - 1 + self.curPiece.MinY()

if not self.TryMove(self.curPiece, self.curX, self.curY):
self.curPiece.SetShape(Tetrominoes.NoShape)
self.timer.Stop()
self.isStarted = False
statusbar.Text = 'Game over'

def TryMove(self, newPiece, newX, newY):
for i in range(4):
x = newX + newPiece.x(i)
y = newY - newPiece.y(i)
if x < 0 or x >= Board.BoardWidth or y < 0 or y >= Board.BoardHeight:
return False
if self.ShapeAt(x, y) != Tetrominoes.NoShape:
return False

self.curPiece = newPiece
self.curX = newX
self.curY = newY
self.Refresh()
return True

def DrawSquare(self, g, x, y, shape):
colors = [ (0, 0, 0), (204, 102, 102),
(102, 204, 102), (102, 102, 204),
(204, 204, 102), (204, 102, 204),
(102, 204, 204), (218, 170, 0) ]

light = [ (0, 0, 0), (248, 159, 171),
(121, 252, 121), (121, 121, 252),
(252, 252, 121), (252, 121, 252),
(121, 252, 252), (252, 198, 0) ]

dark = [ (0, 0, 0), (128, 59, 59),
(59, 128, 59), (59, 59, 128),
(128, 128, 59), (128, 59, 128),
(59, 128, 128), (128, 98, 0) ]

pen = Pen(Color.FromArgb(light[shape], light[shape],
light[shape]), 1)
pen.StartCap = LineCap.Flat
pen.EndCap = LineCap.Flat

g.DrawLine(pen, x, y + self.SquareHeight() - 1, x, y)
g.DrawLine(pen, x, y, x + self.SquareWidth() - 1, y)

darkpen = Pen(Color.FromArgb(dark[shape], dark[shape],
dark[shape]), 1)
darkpen.StartCap = LineCap.Flat
darkpen.EndCap = LineCap.Flat

g.DrawLine(darkpen, x + 1, y + self.SquareHeight() - 1,
x + self.SquareWidth() - 1, y + self.SquareHeight() - 1)
g.DrawLine(darkpen, x + self.SquareWidth() - 1,
y + self.SquareHeight() - 1, x + self.SquareWidth() - 1, y + 1)

g.FillRectangle(SolidBrush(Color.FromArgb(colors[shape], colors[shape],
colors[shape])), x + 1, y + 1, self.SquareWidth() - 1,
self.SquareHeight() - 2)

pen.Dispose()
darkpen.Dispose()

class Shape(object):
coordsTable = (
((0, 0),     (0, 0),     (0, 0),     (0, 0)),
((0, -1),    (0, 0),     (-1, 0),    (-1, 1)),
((0, -1),    (0, 0),     (1, 0),     (1, 1)),
((0, -1),    (0, 0),     (0, 1),     (0, 2)),
((-1, 0),    (0, 0),     (1, 0),     (0, 1)),
((0, 0),     (1, 0),     (0, 1),     (1, 1)),
((-1, -1),   (0, -1),    (0, 0),     (0, 1)),
((1, -1),    (0, -1),    (0, 0),     (0, 1))
)

def __init__(self):
self.coords = [[0,0] for i in range(4)]
self.pieceShape = Tetrominoes.NoShape

self.SetShape(Tetrominoes.NoShape)

def GetShape(self):
return self.pieceShape

def SetShape(self, shape):
table = Shape.coordsTable[shape]
for i in range(4):
for j in range(2):
self.coords[i][j] = table[i][j]

self.pieceShape = shape

def SetRandomShape(self):
rand = Random()
self.SetShape(rand.Next(1, 7))

def x(self, index):
return self.coords[index]

def y(self, index):
return self.coords[index]

def SetX(self, index, x):
self.coords[index] = x

def SetY(self, index, y):
self.coords[index] = y

def MaxX(self):
m = self.coords
for i in range(4):
m = max(m, self.coords[i])

return m

def MinY(self):
m = self.coords
for i in range(4):
m = min(m, self.coords[i])

return m

def RotatedLeft(self):
if self.pieceShape == Tetrominoes.SquareShape:
return self

result = Shape()
result.pieceShape = self.pieceShape
for i in range(4):
result.SetX(i, self.y(i))
result.SetY(i, -self.x(i))

return result

def RotatedRight(self):
if self.pieceShape == Tetrominoes.SquareShape:
return self

result = Shape()
result.pieceShape = self.pieceShape
for i in range(4):
result.SetX(i, -self.y(i))
result.SetY(i, self.x(i))

return result

class IForm(Form):

def __init__(self):
self.Text = 'Tetris'
self.Width = 200
self.Height = 430
self.FormBorderStyle = FormBorderStyle.FixedSingle
board = Board()
board.Width = 195
board.Height = 380

self.statusbar = StatusBar()
self.statusbar.Parent = self
board.Start()
self.CenterToScreen()

Application.Run(IForm())
```

I have simplified the game a bit, so that it is easier to understand. The game starts immediately, after it is launched. We can pause the game by pressing the p key. The space key will drop the tetris piece immediately to the bottom. The d key will drop the piece one line down. (It can be used to speed up the falling a bit.) The game goes at constant speed, no acceleration is implemented. The score is the number of lines that we have removed.

```class Tetrominoes(object):
NoShape = 0
ZShape = 1
SShape = 2
LineShape = 3
TShape = 4
SquareShape = 5
LShape = 6
MirroredLShape = 7
```

There are seven different types of tetrominoes.

```...
self.curX = 0
self.curY = 0
self.numLinesRemoved = 0
self.board = []
...
```

Before we start the game cycle, we initialize some important variables. The `self.board` variable is a list of `Tetrominoes`. It represents the position of various shapes and remains of the shapes on the board.

```def ClearBoard(self):
for i in range(Board.BoardHeight * Board.BoardWidth):
self.board.append(Tetrominoes.NoShape)
```

The `ClearBoard()` method clears the board. It fills the `self.board` variable with `Tetrominoes.NoShape` values.

Painting in the tetris game is done in the `OnPaint()` method.

```for i in range(Board.BoardHeight):
for j in range(Board.BoardWidth):
shape = self.shapeAt(j, Board.BoardHeight - i - 1)
if shape != Tetrominoes.NoShape:
self.drawSquare(g,
0 + j * self.squareWidth(),
boardTop + i * self.squareHeight(), shape)
```

The painting of the game is divided into two steps. In the first step, we draw all the shapes, or remains of the shapes that have been dropped to the bottom of the board. All the squares are rememberd in the `self.board` list. We access it using the `ShapeAt()` method.

```if self.curPiece.shape() != Tetrominoes.NoShape:
for i in range(4):
x = self.curX + self.curPiece.x(i)
y = self.curY - self.curPiece.y(i)
self.drawSquare(g, 0 + x * self.squareWidth(),
boardTop + (Board.BoardHeight - y - 1) * self.squareHeight(),
self.curPiece.shape())
```

The next step is drawing of the actual piece that is falling down.

In the `OnKeyUp()` method we check for pressed keys.

```elif key == Keys.Left:
self.tryMove(self.curPiece, self.curX - 1, self.curY)
```

If we press the left arrow key, we try to move the piece to the left. We say try, because the piece might not be able to move.

In the `TryMove()` method we try to move our shapes. If we cannot move the piece, we return False.

```for i in range(4):
x = newX + newPiece.x(i)
y = newY - newPiece.y(i)
if x < 0 or x >= Board.BoardWidth or y < 0 or y >= Board.BoardHeight:
return False
if self.ShapeAt(x, y) != Tetrominoes.NoShape:
return False
```

If the shape is at the edge of the board or is adjacent to some other piece, we return False.

```self.curPiece = newPiece
self.curX = newX
self.curY = newY
self.Refresh()
return True
```

Otherwise we place the current falling piece to a new position and return True.

```def OnTick(self, sender, event):

if self.isWaitingAfterLine:
self.isWaitingAfterLine = False
self.NewPiece()
else:
self.OneLineDown()
```

In the `OnTick()` method we either create a new piece, after the previous one hit the bottom, or we move a falling piece one line down.

If the piece hits the bottom, we call the `RemoveFullLines()` method. First we find out all full lines.

```rowsToRemove = []
for i in range(Board.BoardHeight):
n = 0
for j in range(Board.BoardWidth):
if not self.ShapeAt(j, i) == Tetrominoes.NoShape:
n = n + 1
if n == 10:
rowsToRemove.append(i)
```

We cycle throught the board. A row can have ten pieces of shapes. If the row is full, e.g. n is equal to 10, we store the line number for later removal.

```rowsToRemove.reverse()

for m in rowsToRemove:
for k in range(m, Board.BoardHeight):
for l in range(Board.BoardWidth):
self.SetShapeAt(l, k, self.ShapeAt(l, k + 1))
```

These code lines remove the full lines. We reverse the order of the `rowsToRemove` list so that we begin with the bottom most full line. What we do is remove a full line by placing all lines about it one line down. This happens for all full lines In our case we use a naive gravity. This means that the pieces may be lef floating above empty gaps.

```def NewPiece(self):
self.curPiece = self.nextPiece
statusbar = self.Parent.statusbar
self.nextPiece.SetRandomShape()
self.curX = Board.BoardWidth / 2 + 1
self.curY = Board.BoardHeight - 1 + self.curPiece.MinY()

if not self.TryMove(self.curPiece, self.curX, self.curY):
self.curPiece.SetShape(Tetrominoes.NoShape)
self.timer.Stop()
self.isStarted = False
statusbar.Text = 'Game over'
```

The `NewPiece()` method creates randomly a new tetris piece. If the piece cannot go into its initial position, e.g. the `TryMove()` method returns False, the game is over.

```colors = [ (0, 0, 0), (204, 102, 102),
... ]

light = [ (0, 0, 0), (248, 159, 171),
... ]

dark = [ (0, 0, 0), (128, 59, 59),
... ]
```

There are three lists of colours. The `colours` list stores color values for the fills of the squares. Each of seven pieces has its own color. The `light` and the `dark` store colours for lines that will make the square look 3D. These colours are the same, just are lighter and darker. We will draw two lines with light colour to the top and left sides of the squares and two lines with darker colour to the right and bottom sides.

```g.DrawLine(pen, x, y + self.SquareHeight() - 1, x, y)
g.DrawLine(pen, x, y, x + self.SquareWidth() - 1, y)
```

These two lines draw the light lines for a square.

The `Shape` class saves information about the tetris piece.

```self.coords = [[0,0] for i in range(4)]
```

Upon creation we create an empty coordinates list. The list will save the coordinates of the tetris piece. For example, these tuples (0, -1), (0, 0), (1, 0), (1, 1) represent a rotated S-shape. The following diagram illustrates the shape.

When we draw the current falling piece, we draw it at `self.curX`, `self.curY` position. Then we look at the coordinates table and draw all the four squares.

The `RotateLeft()` method rotates a piece to the left.

```if self.pieceShape == Tetrominoes.SquareShape:
return self
```

If we have the `Tetrominoes.SquareShape` piece, we do nothing. This shape is always the same.

```result = Shape()
result.pieceShape = self.pieceShape
for i in range(4):
result.SetX(i, self.y(i))
result.SetY(i, -self.x(i))

return result
```

In other cases, we change coordinates of the piece. To understand this code, look at the above figure.