//task12
//rules:
//if the box (you) is hit by one of the flowers, you lose one life,
//if the box (you) is hit by one of the circles (stones), you gain one life,
//you could "jump" so to avoid hit by them
//choose to use key or mouse:
//click on the button at lower right to switch between key or mouse modes.
//using keyborad:
//use the arrow keys (left / right / up / down) on the keyboard to control the
box's (the "gun") movement,
//use space bar to make it jump
//using mouse:
//move the mouse to navigate the box,
//left click to jump