diff --git a/src/main.ts b/src/main.ts
index 7c97918..1a63996 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -2,32 +2,38 @@ import { line, type Line, group, translate, asSvg, svgDoc, scale, flip } from "@
 import { vec2, type Vec2 } from "@thi.ng/vectors"
 import { $canvas } from "@thi.ng/rdom-canvas";
 import { reactive, sync } from "@thi.ng/rstream";
-import { $compile, $input } from '@thi.ng/rdom'
+import { $compile, $input, $inputNum } from '@thi.ng/rdom'
 import { cycle, comp, range, iterator, map, mapcat, reverse, zip } from "@thi.ng/transducers"
 
-const cellSize_ = "12"
-const xs_ = "101110100101100"
-const ys_ = "101001111001110000101"
+// initial settings
 
-const parsePattern = (pattern: string) => pattern.split('').map(x => Number.parseInt(x, 10))
+// available size for a2: 420 * 594
+const width_ = 420
+const height_ = 594
+const cellSize_ = 12
 
-const xSeeds = reactive(xs_).map((pattern) => parsePattern(pattern))
-const ySeeds = reactive(ys_).map((pattern) => parsePattern(pattern))
-const cellSize = reactive(cellSize_).map(num => {
-  const next = Number.parseInt(num, 10)
-  return Number.isNaN(next)|| next < 5 ? 5 : next
-})
+const xSeeds_ = "101110100101100"
+const ySeeds_ = "101001111001110000101"
+const unit_ = 'mm'
+
+// turn these into reactive values to trigger re-rendering on change
+
+const width = reactive(width_)
+const height = reactive(height_)
+const unit = reactive(unit_)
+const size = sync({ src: { width, height } }).map(({ width, height }) => [width, height])
+
+const toNumber = (v: any) => typeof v === 'number' ? v : Number.parseInt(v, 10)
+const parsePattern = (pattern: string) => pattern.split('').map(toNumber)
+
+const xSeeds = reactive(xSeeds_).map((pattern) => parsePattern(pattern))
+const ySeeds = reactive(ySeeds_).map((pattern) => parsePattern(pattern))
+const cellSize = reactive(cellSize_).map(num => Number.isNaN(num) || num < 5 ? 5 : num) // restrict cells to be at least 5 $unit
 
 // const backgroundColor = getComputedStyle(document.documentElement).getPropertyValue('--background-color')
 const primaryColor = getComputedStyle(document.documentElement).getPropertyValue('--primary-color')
 const secondaryColor = getComputedStyle(document.documentElement).getPropertyValue('--secondary-color')
 
-// available size for a2: 420 * 594
-const width = 420
-const height = 594
-
-const size = [width, height]
-
 // some explanation for what's happening below:
 //
 // - a coord is a position on a single axis
@@ -71,8 +77,19 @@ const generateLines = (maxCoordOnAxis: number, maxCoordPerpendicular: number, se
 // now we can put the functions above together based on the current settings and generate a scene to be drawn
 
 const scene = sync({
-  src: { cellSize, xSeeds, ySeeds, }
-}).map(({ cellSize, xSeeds, ySeeds }) => {
+  src: {
+    size,
+    cellSize,
+    xSeeds,
+    ySeeds,
+  }
+}).map(({
+  size,
+  cellSize,
+  xSeeds,
+  ySeeds,
+}) => {
+  const [width, height] = size
   const minPadding = cellSize
 
   // calculate available drawing area
@@ -85,15 +102,13 @@ const scene = sync({
   const xLines = [...map(l => scale(l, cellSize), generateLines(yCells, xCells, cycle(ySeeds), xLineGen))]
   const yLines = [...map(l => scale(l, cellSize), generateLines(xCells, yCells, cycle(xSeeds), yLineGen))]
 
-  const scene = translate(
+  return translate(
     group(
       { __background: primaryColor, stroke: secondaryColor },
       [...yLines, ...xLines]
     ),
     [xPadding, yPadding]
   )
-
-  return scene
 })
 
 const input = (label: string, attrs: any) =>
@@ -106,25 +121,47 @@ $compile(
     $canvas(scene, size)],
    ["aside", {},
     ["h2", {}, "Settings"],
+    input("Canvas width:", {
+      type: "number",
+      min: "10",
+      value: width.deref()!,
+      oninput: $inputNum(width),
+    }),
+    input("Canvas height:", {
+      type: "number",
+      min: "10",
+      value: height.deref()!,
+      oninput: $inputNum(height),
+    }),
     input("Grid size: ", {
       type: "number",
       min: "5",
       value: cellSize.deref()!,
-      oninput: $input(cellSize)
+      oninput: $inputNum(cellSize),
     }),
     input("X Pattern: ", {
       type: "text",
-      value: xs_,
+      value: xSeeds_,
       oninput: $input(xSeeds)
     }),
     input("Y Pattern: ", {
       type: "text",
-      value: ys_,
+      value: ySeeds_,
       oninput: $input(ySeeds)
     }),
     ["h2", {}, "SVG Export"],
     ["div", {}, ["textarea", {
-      value: scene.map((scene) => asSvg(svgDoc({ viewBox: `0 0 ${size[0]} ${size[1]}` }, scene))),
+      value: sync({
+        src: {
+          scene,
+          size,
+          unit,
+        }
+      }).map(({
+        scene,
+        size,
+        unit
+      }) => asSvg(svgDoc({ width: `${size[0]}${unit}`, height: `${size[1]}${unit}`, viewBox: `0 0 ${size[0]} ${size[1]}` }, scene))),
       cols: 80,
       rows: 20
     }]]]]