void setup()
{
size(450,700);

for (int i = 0; i < 9; i++)
{
for (int j = 0; j < 9; j++)
{
fill(255,255,255);
rect(i*50,j*50,50,50);
}
}

}

void draw()
{

}

void mousePressed() 
{

for (int i = 0; i < 9; i++)
{
for (int j = 0; j < 9; j++)
{

if (mouseX > i*50 && mouseX < i*50 + 50 && mouseY > j*50 && mouseY < j*50+50 )
{
fill(204, 102, 0);

text("click", i*50 + 20, j*50 + 25);
}
}
} 
}