RicEditor tutorial: Create a cannon game!

Moving the bullet

In this game we want to fire a bullet when we press the ENTER button. We are going to use the same principle as for the falling stone: we use the counter inside a WHILE structure and let it count from 0 to 64. The difference is of course that we must start the WHILE structure when the ENTER button is pressed. First we start with a “outside” WHILE structure, and make sure to wire the loop condition to the local variable Game over.
Movingbulletloop

So we insert a sensor command found in NXT I/O:

read_sensor

We insert this command and select red NXT Buttons:
select NXT buttons

We go back to the block diagram:

NXT_Button_Addded

Since this command by default is set to check for the ENTER button, we don’t need to set what button to check. The output from this command is yes if the button is pressed (TRUE) or no (FALSE) otherwise. This value we’ll send to a CASE structure. We find the CASE structure in the menu NXT Programming/Structure/Case Structure;

CaseMenu

We insert this and wire it to the NXT Button command:

CASEInserted

So let’s insert a WHILE structure in the TRUE part of the Case structure:

WHILE_loop_added

We want to use the counter to move the bullet. We insert a local variable found in NXT Programming/Structures:
localvariable menu

So we insert a local variable in this inner WHILE structure:

Local inserted

When it is inserted we move the mouse-pointer on it, right-click and the select Ybullet:

SelectYbullet

The local variable is configured to WRITE:

Ybulletconfigurd

We wire the local variable to the counter (the blue I in the lower left corner):

Ybulletwired

The Y coordinate for the bullet will increase with 1 for each time the loop runs. But when it is greater than 64 it is at the top of the NXT screen and then we must terminate the WHILE structure. We insert a Greater? command found in NXT Programming/Comparison:

greaterORequal

Inserted it looks as below:

greaterthanadded_1

We wire the upper left corner to the wire connected to the counter:

counterconnectedtogreaterthan

For the lower left corner we right-click and select Create constant. We set the value to 64:

64constantadded

It is easy think we now must wire the right corner of the Greater? command to the stop sign. But remember, the bullet must also stop when it hit the falling stone. We need to insert the local variable HIT? found in NXT Programming/Structures:

localvariable menu

We right-click the local variable and select HIT? from the list:

SelectHIT

We have to change this local variable to read. Right-click and select Change To Read:

HIT Change to read

Since both conditions (YBullet>64 and the fact that the bullet has hit the stone) should terminate the WHILE structure, we must insert an OR command found in NXT Programming/Boolean:

OR Menu

We insert this and wire both conditions as shown below:

OR Wired

Finally we wire the output of the OR command to the red stop sign (the condition terminal):

STOP Wired

To slow down the bullet we insert a wait for msecs and set it to 15 msecs. This we have done before, it should now look like this:

wait 15msecs

Our loop is now finished!

 

Related posts

Add a comment

You must be logged in to comment.