Clarify & speed up basic views tutorial

[pushfoo]

• Reduce coin count from 50 to 25 (focus is on views, not the game)

[Ibrahim2750mi]

LGTM!

[pushfoo]

@pvcraven for context, the direction I'm leaning towards for this would be to move this under a "Screens & Menus with Views" headings akin to the shaders index we currently have.

I may want to have #1608 expand on it, but I'm not sure yet. What I am sure of is that 50 coins takes far too long to play through for a tutorial which is about the screens, not the gameplay.

[pushfoo]

@pvcraven any objections to replacing code like this:

sprite.center_x=10sprite.center_y=10

with more efficient code which doesn't update the SpriteList twice?

sprite.position=10, 10

Also sorry for the close / re-open. I had a touchpad issue.

[pvcraven]

@pvcraven any objections to replacing code like this:

sprite.center_x=10sprite.center_y=10

with a more efficient code which doesn't update the SpriteList twice?

sprite.position=10, 10

No. Some examples that are super-basic I avoid that because students might not be introduced to tuples yet. But by the time they use screens, shouldn't be an issue.