Making of Tetris Game in C

Block types in tetris

Have you ever tried to make tetris game in c. Tetris is a simple game with minimal graphics. It is much easy to program in c. If you are not familiar with graphics.h header file, you may think it almost impossible. But, graphics.h is just a simple library justs as string.h. It is very simple to learn. Let us first see how to represent tetris as data structure. There are mainly 5 types of blocks in tetris. They are L blocks, Z blocks, I blocks, S blocks and T blocks. The blocks are shown in the picture.


To make the tetris game, we first make a two dimensional array. An element in this integer array is a single block (one of the four blocks in each block type) in the game. We set all the elements to zero initially to show that the matrix is empty. We may call each element a cell. So to represent a Z block, we need four cells. In the matrix, to represent a falling block (eg: a Z block) we set corresponding elements' values to 1. We move these 1's in the 2d integer array downwards to simulate falling. Then when it reaches bottom, these 1's are changed to 2's. This is to denote that these cell cannot be moved further. Again, we start another random block from the top (first row).

We manipulate the array to represent each actions in the tetris. The following program lets you understand things easily. In the program, for random spawning of new falling blocks, we use random function with current time as seed.

#include<stdio.h>
#include<stdlib.h>
#include<graphics.h>
#include<time.h>

//The tetris matrix (2d array)

int board[35][13];

//Different versions of T block (rotated)
int t_[8]={1,0,1,1,1,2,2,1};
int t_90[8]={0,1,1,0,1,1,2,1};
int t_180[8]={0,1,1,0,1,1,1,2};
int t_270[8]={0,1,1,1,1,2,2,1};

//Different versions of L block (rotated)

int l_[8]={0,2,1,0,1,1,1,2};
int l_90[8]={0,1,1,1,2,1,2,2};
int l_180[8]={1,0,1,1,1,2,2,0};
int l_270[8]={0,0,0,1,1,1,2,1};

//S block
int s_[8]={0,0,0,1,1,0,1,1};

//Different versions of Z block

int z_[8]={1,1,1,2,2,0,2,1};
int z_90[8]={0,1,1,1,1,2,2,2};

//Different versions of I block
int i_ver[8]={0,1,1,1,2,1,3,1};
int i_hor[8]={1,0,1,1,1,2,1,3};

//score as string
char * scorestr;

/*
Numbering for type of blocks:
(values of fallingBlockNumber)
0=T
1=L
2=S
3=Z
4=I
*/

//pointer to current falling block type array

int *blockarray;
int fallingblockNum;
int fallingBlockVersion=0;//values 0 to 4
int fallingBlockRow=0;//the current row of falling block
int fallingBlockCol=0;//the current column of falling block
int startdelay=200;
int motiondelay;
int scoreInc=5;//score for each line clearance
int myscore=0;//score

//spawning next falling block
void NextBlock()
{
fallingblockNum=rand()%5;
if(fallingblockNum==0||fallingblockNum==1)
 fallingBlockVersion=rand()%4;
else if(fallingblockNum==4||fallingblockNum==3)
 fallingBlockVersion=rand()%2;
else
 fallingBlockVersion=0;
fallingBlockRow=0;
fallingBlockCol=5;
}

//store pointer to current falling block's array in *blockarray;
int *getFallingBlockArray()
{
int a=fallingblockNum*10+fallingBlockVersion;
switch(a)
    {
    case 0:return ((int*)&t_);
    case 1:return ((int*)&t_90);
    case 2:return ((int*)&t_180);
    case 3:return ((int*)&t_270);
    case 10:return ((int*)&l_);
    case 11:return ((int*)&l_90);
    case 12:return ((int*)&l_180);
    case 13:return ((int*)&l_270);
    case 20:return ((int*)&s_);
    case 30:return ((int*)&z_);
    case 31:return ((int*)&z_90);
    case 40:return ((int*)&i_hor);
    case 41:return ((int*)&i_ver);
    }
return ((int*)&i_ver);
}

/* To check if moving to left or right

or rotation of falling block is feasible.

i.e to check whether there is enough space around it.

*/
int isDrawable(int newrow,int newcol,int blockversion)
{
int i,tempversion,flag=1;;
tempversion=fallingBlockVersion;
fallingBlockVersion=blockversion;
blockarray=getFallingBlockArray();

for(i=0;i<8;i+=2)
    {

//check if block goes out of the matrix (up or down)
if(newrow+blockarray[i]>34||newrow+blockarray[i]<0)
 {
 flag=0;
 break;
 }

//check if block goes out of the matrix (left or right)
if(newcol+blockarray[i+1]>12||newcol+blockarray[i+1]<0)
 {
 flag=0;
 break;
 }

//check if there is any obstacle on the proposed position
if(board[(newrow+blockarray[i])][(newcol+blockarray[i+1])]==2)
 {
 flag=0;
 break;
 }
    }
fallingBlockVersion=tempversion;
blockarray=getFallingBlockArray();
return flag;
}

/*

To clear the old position of falling block

after it moves to a new position (row/column change)

or after it is rotated

*/

void clearOldBlockVersion()
{
int i,r,c;
for(i=0;i<8;i+=2)
 {
 r=fallingBlockRow+blockarray[i];
 c=fallingBlockCol+blockarray[i+1];
 board[r][c]=0;
 setfillstyle(EMPTY_FILL,BLACK);
 setcolor(BLACK);
 bar(2+c*13,2+r*13,2+c*13+13,2+r*13+13);
 rectangle(2+c*13,2+r*13,2+c*13+13,2+r*13+13);
 }
}

/*
To draw the new picture
after it moves to a new position (row/column change)
or after it is rotated
*/
void drawNewBlockVersion()
{
int i,r,c;
for(i=0;i<8;i+=2)
 {
 r=fallingBlockRow+blockarray[i];
 c=fallingBlockCol+blockarray[i+1];
 board[r][c]=1;
 setfillstyle(XHATCH_FILL,CYAN);
 setcolor(GREEN);
 bar(2+c*13,2+r*13,2+c*13+13,2+r*13+13);
 rectangle(2+c*13,2+r*13,2+c*13+13,2+r*13+13);
 }
}

/*
To check whether game is over.
called after every move.
Game is over when tetris matrix is filled.
*/

int isGameOver()
{
if(isDrawable(0,5,fallingBlockVersion)==0)
    return 1;
drawNewBlockVersion();
if(isAtBottom())
    return 1;
return 0;
}

/*

To check if falling block reached the bottom

*/
int isAtBottom()
{
int i,max=0,ti,tj;
for(i=0;i<8;i+=2)
    if(*(blockarray+i)>max)
 max=*(blockarray+i);
if(fallingBlockRow+max>=34)
 return 1;
for(i=0;i<8;i+=2)
    {
    ti=*(blockarray+i)+fallingBlockRow;
    tj=*(blockarray+i+1)+fallingBlockCol;
    if(board[ti+1][tj]==2)
       return 1;
    }
return 0;
}

/*

Draw score on screen

*/
void showScore()
{
int left,top;
setcolor(BLACK);
setfillstyle(EMPTY_FILL,BLACK);
left=getmaxx()-100;
top=getmaxy()/2;
bar3d(left,top,left+60,top+70,2,1);
setcolor(YELLOW);
settextstyle(TRIPLEX_FONT, HORIZ_DIR,2);
outtextxy(getmaxx()-100,getmaxy()/2,"Score: ");
outtextxy(getmaxx()-100,getmaxy()/2+20,itoa(myscore,scorestr,10));
}

/*
To clear any row that is fully filled and increment score.
Also settles rows over the cleared row down.
*/
void CollapseFullRow()
{
int i,j,k,sum,copyskipover=0,r;
for(i=34;i>=0;)
    {
    sum=0;//full flag
    for(j=0;j<13;j++)
 sum+=board[i][j];
    if(sum==2*13)//row full
 {
 myscore+=scoreInc;
 copyskipover++;
 }
    if(sum==0)
 break;
    i--;
    if(copyskipover>0)
 {
 for(j=0;j<13;j++)
     {
     r=i+copyskipover;
     board[r][j]=board[i][j];
     if(board[i][j]==0)
  {
  setfillstyle(EMPTY_FILL,BLACK);//empty yo hatch
  setcolor(BLACK);
  bar(2+j*13,2+r*13,2+j*13+13,2+r*13+13);
  }
     else
  {
  setfillstyle(XHATCH_FILL,CYAN);
  setcolor(GREEN);
  bar(2+j*13,2+r*13,2+j*13+13,2+r*13+13);
  rectangle(2+j*13,2+r*13,2+j*13+13,2+r*13+13);
  }
     }
 }
    }
for(k=0;k<copyskipover;k++)
    {
    r=i+k;
    for(j=0;j<13;j++)
 {
 board[r][j]=0;
 setfillstyle(XHATCH_FILL,BLACK);
 setcolor(BLACK);
 bar(2+j*13,2+r*13,2+j*13+13,2+r*13+13);
 }
    }
showScore();
}

//function to display game over and end game

void GameOver();

void main()
{
int scorespeedctrl=0;
char arrowpre,ch,timehalving=0;
int gd=DETECT,gm,i,j,k=1,spawn=1,tversion;
motiondelay=startdelay;
scorestr=(char*)malloc(sizeof(char)*10);
for(i=0;i<35;i++)
    for(j=0;j<13;j++)
 board[i][j]=0;

/*

to get the ascii characters for up arrow key.

When any of arrow key is pressed, two characters

are sent to buffer. The first one may be different

on different compilers and systems.

The second one is of value 72 for up arrow.

*/
while(k!=72)
{
printf("press 'up' arrow key to start\n");
arrowpre=getch();
if(kbhit())
 k=getch();
}

initgraph(&gd,&gm,"C:\\TURBOC3\\BGI\\");
cleardevice();
setcolor(YELLOW);
rectangle(0,0,13*13+6,35*13+6);
srand(time(NULL));
showScore();
setcolor(RED);
settextstyle(SMALL_FONT, HORIZ_DIR,6);
outtextxy(getmaxx()-200,getmaxy()/2-100,"Press 'Q' to quit.");

while(ch!='q'&&ch!='Q'&&k!='q'&&k!='Q')
    {
    if(kbhit()&&spawn==0)
 {
 ch=getch();
 if(ch==arrowpre)//if an arrow key pressed
     {
     k=getch();
     if(k==72)//if up arrow key is pressed
  {
  if(fallingblockNum==0||fallingblockNum==1)
      tversion=(fallingBlockVersion+1)%4;
  else if(fallingblockNum==4||fallingblockNum==3)
      tversion=(fallingBlockVersion+1)%2;

  if(fallingblockNum!=2&&isDrawable(fallingBlockRow,fallingBlockCol,tversion))
      {
      clearOldBlockVersion();
      fallingBlockVersion=tversion;
      blockarray=getFallingBlockArray();
      drawNewBlockVersion();
      }
  }
     else if(k==75)//if left arrow key is pressed

  {
  if(isDrawable(fallingBlockRow,fallingBlockCol-1,fallingBlockVersion))
      {
      clearOldBlockVersion();
      fallingBlockCol--;
      drawNewBlockVersion();
      }
  }
     else if(k==77)//if right arrow key is pressed
  {
  if(isDrawable(fallingBlockRow,fallingBlockCol+1,fallingBlockVersion))
      {
      clearOldBlockVersion();
      fallingBlockCol++;
      drawNewBlockVersion();
      }
  }
     else if(k==80)//if down arrow key is pressed
  {
  if(isDrawable(fallingBlockRow+1,fallingBlockCol,fallingBlockVersion))
      {
      clearOldBlockVersion();
      fallingBlockRow++;
      drawNewBlockVersion();
      }
  }
     while(kbhit())
  getch();
     }
 }
    if(isAtBottom()&&spawn==0)
 {
 for(i=0;i<8;i+=2)
     {
     board[fallingBlockRow+blockarray[i]][fallingBlockCol+blockarray[i+1]]=2;
     }
 spawn=1;
 CollapseFullRow();
 }
    if(spawn)
 {
 NextBlock();
 blockarray=getFallingBlockArray();
 spawn=0;
 if(isGameOver())
     {
     GameOver();
     return;
     }
 }
    else
 {
 timehalving=(timehalving+1)%3;
 if(timehalving==2)
  {
  clearOldBlockVersion();
  fallingBlockRow++;
  drawNewBlockVersion();
  }
 }
    scorespeedctrl=(scorespeedctrl+1)%280;
    if(scorespeedctrl==0)
 {
 motiondelay-=8;
 scoreInc++;
 }
    delay(motiondelay);
    }
}

void GameOver()
{
static int style=TRIPLEX_FONT;
static int size = 4;
setcolor(YELLOW);
settextjustify(CENTER_TEXT, CENTER_TEXT);
settextstyle(style, HORIZ_DIR, size);
outtextxy(getmaxx()/2-10,getmaxy()/2,"Game Over.\n");
getch();
main();
}