Programming games Share your plans for your virtual

Programming games Share your plans for your virtual something. Homework: Catch up. Complete your virtual something.

Function • Functions are one or more statements packaged together defined to be used later. • The format for defining a function in Java. Script is – function – the_name_given_by_programmer – (zero, or some number of names for parameters) –{ – One or more statements – }

Example • function convert. Cto. F (cen) { return cen*(9. 0/5. 0) + 32. 0; } • Look back at examples with init, toss, change

Calling a function • Aka invoking, executing • Various ways, including – By itself as a statement: startup(); – In an expression: total = cost + ctax(cost); – As value of attribute in html tag, these set up a call for later • • – As event handler • td = set. Interval(moveit, 100); • canvas 1. add. Event. Listener("click", toss, false);

Recommend • Review the code for your projects and notice use of functions. • Look up functions online • Go to Library and look at my books on reserve • Try codeacademy

Planning • … is a good thing to do! • It is real work. • Formal systems / commercial products for systems design • Note: most work is not 'green fields', ab initio… but enhancements & fixes.

Share plans for virtual something • ? ? ?

Discrete simulation • Discrete as opposed to continuous. • Determinations / calculations done at timed intervals – using set. Interval • Reference & modify internal variables • May change images (src of img elements) • May change canvas

State Variables • values with names • Global – outside of any function and so accessible by all functions – persistent: stay around • My Virtual Dog: weight of the dog. • You may have more than 1 state variable. • You also may have information in form fields or other html displayed to the viewer/player.

Checking conditions You can use • if statements including nested if statements • switch statements

Jargon • Stochastic: factor involving some level of chance. – Note: In my virtual dog, the formula varied from being 10% likely to produce snarly dog to 90% likely. • Discrete simulation: calculations done at fixed intervals of time. NOT continuously. • Persistent: stays around… Applied to variables. Global variables, variables with var statement outside of any function, stay around…

Size of images • An img tag can include width and/or height attributes OR NOT – If nothing specified, the width and height of the image file is used. – If just width or just height, the other is calculated to keep aspect ratio. • It makes sense to set at least height in the slideshow. • Pixel is a small unit of length on the screen. • Experiment !

Recommended • Style section formatting • Script section for dynamic behavior • Body section for content (structured content)

Virtual something: Keep it simple, … At least for now: • At least 2 actions • No more states than my virtual dog, and it can be less. • Focus on logic. Can improve graphics later.

General point • What is the minimum you need to do to test your plan? – Do this first and then add…. • 3 -4 images in slide show • 3 states, 1 action in virtual something • What is the minimum you need to do to satisfy the assignment? – 3 -4 images in slide show – 5 -6 states, 2 actions, 1 stochastic factor, …

[partial] Ideas Perhaps for midterm project: • combine virtual something with credit card? – Man goes into a bar… • Virtual something be drawn on canvas: easier to vary color, size, and content. – Fill up screen with stars? Something else? • ‘Ville, Sim type game: “buy” stuff. Add stochastic factor?

Misc. • Filezilla is one product that performs FTP (file transfer protocol). There are others. This is what is used here. • On your home computer, consider using Normal, as opposed to Ask for Password • Do keep uploading work and updating your index. html file – Give your virtual project an evocative name, NOT Virtual something

Consider • Having possibility for game lasting forever • OR NOT

Virtual something • To keep a global variable such as weight from going above a certain amount • weight = Math. min(weight, upperlimit); • To keep it from going less than • weight = Math. max(weight, lowerlimit);

Drawing on canvas • May or may not use clear. Rect each time. • Consider using draw. Image and then draw. Image for smaller images on top or begin. Path(), …. stroke() on top – Consider looking up • bezier. Curve. To or quadratic. Curve. To in addition to arc

States • May have parallel arrays holding information such as colors, sizes, positions, image files • START SMALL

Classwork / homework • Get caught up – This includes uploading work and modifying index. html page • Build your virtual something. – Note: you can build on this project for your midterm project.