update doc - close #79

Author: softmarshmallow

docs/figma-gradient.md

@@ -3,7 +3,25 @@
 - [figma paint - gradient paint](https://www.figma.com/plugin-docs/api/Paint/#gradientpaint)
 - [css gradient](https://developer.mozilla.org/en-US/docs/Web/CSS/gradient)
 
-## gradient type
+## Cases
+
+- Gradient fills in Ellipse, Rect, Frame > Standard styles
+- Gradient fills in vector path > SVG / PNG
+- Complex gradient > SVG / PNG
+
+## Understanding Figma Gradient system - It's not like what you think!
+
+Gradient in figma is bit different on render-styling (css) If you have LinearGradient - `[(black 1) at 0%, (red 0) at 100%]` Representation in css would be `linear-gradient(90deg, rgba(0,0,0,1) 0%, rgba(255,0,0,0) 100%);`, you might think. But this is incorrect.
+
+To match a visually identical gradient, you need to have multiple gradient per colors. (Even if it is in a single fill item)
+
+```css
+.single-fill-item {
+  background: linear-gradient(90deg, black, transparent), linear-gradient(90deg, rgba(255, 0, 0, 1), transparent);
+}
+```
+
+**types of gradient**
 
 - linear gradient
 - radial gradient
@@ -50,3 +68,23 @@ background: radial-gradient(red, blue);
 
 > **gradient paint degree**
 > WIP
+
+## Note - Fallbacks on complex gradient
+
+> This is a technical issue, we will add support for complex gradient in the future. [Learn More](https://github.com/gridaco/designto-code/issues/78)
+
+Since perfectly providing a visually identical style code is redundant, we provide a fallback on complex gradient. (svg on web, png(optionally) on flutter)
+
+**Fallback cases**
+
+- when gradient position does not starts from (or ends at) 0% or 100%
+- when gradient is not linear or radial.
+- when not one of the cases
+  - n - s (0°) (supported)
+  - s - n (180°) (supported)
+  - e - w (270°) (supported)
+  - w - e (90°) (supported)
+  - nw - se (directional) (supported)
+  - ne - sw (directional) (supported)
+  - sw - ne (directional) (supported)
+  - se - nw (directional) (supported)