Fix assorted problems in Writing Methods

- Build is updated to versions that work with JVM 21

- Fix errors in styling content

- Generate missing image

Problem reported by Kim Morgan

book/src/main/scala/All.scala

@@ -5,6 +5,7 @@ object All extends App {
   expressive.All
   flowers.All
   fractals.All
+  methods.All
   programs.All
   recursion.All
 }

book/src/main/scala/methods/All.scala

@@ -0,0 +1,6 @@
+package creativescala
+package methods
+
+object All {
+  WritingMethods
+}

book/src/main/scala/methods/WritingMethods.scala

@@ -0,0 +1,27 @@
+package creativescala
+package methods
+
+import doodle.core._
+import doodle.image._
+import doodle.syntax.all._
+import doodle.image.syntax.all._
+import doodle.java2d._
+
+object WritingMethods {
+  def box(color: Color, spin: Angle): Image =
+    Image
+      .rectangle(40, 40)
+      .strokeWidth(5.0)
+      .strokeColor(color.spin(spin + 30.degrees))
+      .fillColor(color.spin(spin))
+
+  def gradientBoxes(color: Color): Image = {
+    box(color, 0.degrees)
+      .beside(box(color, 15.degrees))
+      .beside(box(color, 20.degrees))
+      .beside(box(color, 45.degrees))
+      .beside(box(color, 60.degrees))
+  }
+
+  gradientBoxes(Color.royalBlue).save("methods/gradient-boxes")
+}

book/src/pages/foreword-2.md

@@ -25,3 +25,5 @@ One more thing: the name may change as well! I'm not sure Creative Scala fits th
 The members of ScalaBridge London, with particular mention to the following for reporting bugs and suggesting improvements:
 
 - Jess Gordon
+- Kim Morgan
+

book/src/pages/methods/writing-methods.md

@@ -84,10 +84,10 @@ import doodle.java2d.*
 ```
 ```scala mdoc:silent
 def box(color: Color, spin: Angle): Image =
-  Image.rectangle(40, 40).
-    strokeWidth(5.0).
-    strokeColor(color.spin(spin + 30.degrees)).
-    fillColor(color.spin(spin)) 
+  Image.rectangle(40, 40)
+    .strokeWidth(5.0)
+    .strokeColor(color.spin(spin + 30.degrees))
+    .fillColor(color.spin(spin)) 
 
 def gradientBoxes(color: Color): Image = {
   box(color, 0.degrees) beside 
@@ -100,14 +100,15 @@ def gradientBoxes(color: Color): Image = {
 @:@
 
 
-#### Gradient Concentric Circles {-}
+@:exercise(Gradient Concentric Circles)
 
 Now implement methods to draw a picture similar to @:fref(methods:gradient-concentric-circles).
-You should follow a design similar to `gradientBoxes` to reduce the amount of code you write, but we're not going to give the method skeletons this time---you have to work it out yourself.
+You should follow a design similar to `gradientBoxes` to reduce the amount of code you write, but we're not going to give the method skeletons this time; you have to work it out yourself.
 
-@:figure{ img = "./src/pages/recursion/gradient-concentric-circles.pdf+svg", key = "#fig:methods:gradient-concentric-circles", caption = "Five concentric circles filled with a gradient starting from Royal Blue" }
+@:figure{ img = "gradient-concentric-circles.svg", key = "#fig:methods:gradient-concentric-circles", caption = "Five concentric circles filled with a gradient starting from Royal Blue" }
+@:@
 
-<div class="solution">
+@:solution
 There are a number of different ways to write this. 
 We expect you would have two methods, `circle` and `gradientConcentricCircles` mirroring the design of `box` and `gradientBoxes` above.
 The exact implementation of these two methods, particularly `circle` is where we'll see the most difference.
@@ -131,4 +132,4 @@ def concentricCircles(color: Color): Image = {
 
 We could have made `circle` have separate parameters for the size and spin, but we decided to compute the size and spin from a single number.
 This gives us less flexibility (they cannot vary independently) but more compact code.
-</div>
+@:@

build.sbt

@@ -3,7 +3,7 @@ import laika.config.LaikaKeys
 import laika.theme.Theme
 
 val scala213 = "2.13.11"
-val scala3 = "3.3.0"
+val scala3 = "3.3.1"
 
 ThisBuild / organization := "org.creativescala"
 ThisBuild / organizationName := "Creative Scala"

project/build.properties

@@ -1 +1 @@
-sbt.version = 1.8.2
+sbt.version = 1.9.7