update manual and tests

doc/util.typ

@@ -1,4 +1,5 @@
 #import "/src/lib.typ" as cetz-plot
+#import "/src/cetz.typ"
 
 /// Make the title-page
 #let make-title() = {
@@ -33,30 +34,69 @@
   set text(weight: "bold", left-color)
   show link: set text(left-color)
 
-  block(
+  block({
     place(
       top + left,
       dx: -left-fringe * 22cm + 5mm,
       text(3cm, right-color)[CeTZ]
-    ) +
+    )
     text(3cm)[Plot]
-  )
-  block(
-    v(1cm) +
+  })
+
+  block({
+    v(1cm)
     text(
       20pt,
       authors.map(v => link(v.at(1), [#v.at(0)])).join("\n")
     )
-  )
-  block(
-    v(2cm) +
+  })
+  block({
+    v(2cm)
     text(
       20pt,
       link(
         url,
         [Version ] + [#cetz-plot.version]
       )
     )
-  )
+  })
+
+  block({
+    v(2cm)
+    set text(fill: black)
+    cetz.canvas({
+      cetz-plot.plot(
+        size: (8,5),
+        x-tick-step: calc.pi / 4,
+        x-minor-tick-step: calc.pi / 16,
+        x-grid: "both",
+        x-min: 0, x-max: 2 * calc.pi,
+        x-format: cetz-plot.axes.format.multiple-of,
+
+        y-min: -1, y-max: 1, y-tick-step: 0.5, y-minor-tick-step: 0.1,
+        y-grid: "both",
+        {
+          cetz-plot.add.xy(
+            calc.sin, 
+            domain: (0,2*calc.pi), 
+            label: $y=x$, 
+            line: "raw",
+            samples: 100,
+            epigraph: true,
+          )
+
+          cetz-plot.add.xy(
+            (t)=>calc.pow(calc.sin(t),2),
+            domain: (0, 2* calc.pi), 
+            line: "raw",
+            samples: 100,
+            hypograph: true,
+            label: $sin^2 (x)$
+          )
+        }
+      )
+    })
+  })
+
   pagebreak(weak: true)
 }

src/plot/styles.typ

@@ -44,7 +44,7 @@
   ),
   axis-layer: 2,
   grid-layer: -1,
-  background-layer: 0,
+  background-layer: -2,
   padding: 0,
   tick: (
     fill: none,