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Just set a breakpoint and the debugger will open

It's not an error. It is just not always necessary. If the variables are assigned new values and only used within the method during the current act step, then it is probably best to declare them within the method. Also, if the variable is only used one in the method, it might be best to use the method call to get the value at the time it is needed and forego declaring a variable for it at all. So, with this:

Just raise the price by multiplying by one more than the percentage required. That is, to increase by five percent, multiply by 1.05 (or multiply by 105/100).

ok thank you

There is an act method defined in the greenfoot.World class. You can override it (just like it is done in a class extending greenfoot.Actor) in your TitleScreen class. It is just not provided by the World subclass template as it is when you create a new subclass of Actor.

minnow is of type Actor but, nearest is of type Minnow. You need to typecast minnow as type Minnow in order to set it to nearest. That is, line 13 needs to be as follows: <Code Omitted>Also, your method is supposed to return the nearest minnow; not the last one in the list.

ok thank you

In line 3, you need to typecast the world as a GameWorld object (just as in line 2). To avoid double work, you can set the world to an object reference variable prior to line 2: <Code Omitted>It allowed for the rest to be pretty short as one line, so I combined your lines 2 and 3 as my line 3.

Thanks a lot

This may not be quite so easy to do. Remember that both the asteroids and the rocket are drifting/moving. It may not be enough just to change the direction of a colliding asteroid. In my asteroids scenario, which has shielding implemented, I had both colliding actors change their trajectories with the help of a smooth moving system. You may want to take a look at its codes -- especially the

No.

What have you tried?

great, thank you

Well, get that much done so you have something to work with.

The mouseClicked method does not look for clicks on classes. It looks for clicks on a specific object (or any click when the argument is null). If the code given is in your Block class you can use this as the argument. For the world, you can simply use getWorld() for the argument.