创建一个简单的互动填色应用，让用户可以从一系列手绘图像中选择，并使用多种鲜艳的颜色为其上色。

第一屏
1. 显示缩略图：展示提供图像的缩略图，方便导航：
   - 图片1：[动物园动物](https://img.freepik.com/free-vector/hand-drawn-zoo-animals-illustration_23-2151199715.jpg)
   - 图片2：[第二组动物园动物](https://img.freepik.com/free-vector/hand-drawn-zoo-animals-illustration_23-2151199718.jpg)
   - 图片3：[狮子与长颈鹿](https://img.freepik.com/premium-vector/lion-giraffe-hand-drawn_185029-508.jpg)
   - 图片4：[猫头鹰轮廓](https://img.freepik.com/free-vector/hand-drawn-owl-outline-illustration_23-2149277379.jpg)
   - 图片5：[狐狸轮廓](https://img.freepik.com/free-vector/hand-drawn-fox-outline-illustration_23-2149272718.jpg)
   - 图片6：[狮子轮廓](https://img.freepik.com/free-vector/hand-drawn-lion-outline-illustration_23-2149285355.jpg)
   - 图片7：[企鹅轮廓](https://img.freepik.com/free-vector/hand-drawn-penguin-outline-illustration_23-2150582038.jpg)
   - 图片8：[长颈鹿涂鸦](https://img.freepik.com/free-vector/animal-doodle-outline-cute-giraffe_1308-81895.jpg)

缩略图应小巧且可点击，方便跳转到填色页面。

选择图片后
2. 图片展示：全屏显示选中的图片，并垂直居中。

3. 功能按钮：
   - 返回按钮（左上角）：弹出确认对话框——“确定要返回吗？未保存的更改将会丢失。”，然后返回缩略图页面。
   - 保存按钮（左上角）：将当前已上色的图片保存为 PNG 文件。
   - 调色板（右上角）：显示一个大红色圆圈表示当前颜色；点击后打开一个包含24种鲜艳颜色的全屏调色板。

填色交互
4. 填充区域：用户点击或触碰图像边界内的区域，即可使用选定颜色进行填充。

颜色选择应提供丰富体验，界面简单，鼓励创意发挥。

Create a simple interactive coloring application:
First screen:
- Display thumbnails of the provided images:
  1. https://img.freepik.com/free-vector/hand-drawn-zoo-animals-illustration_23-2151199715.jpg
  2. https://img.freepik.com/free-vector/hand-drawn-zoo-animals-illustration_23-2151199718.jpg
  3. https://img.freepik.com/premium-vector/lion-giraffe-hand-drawn_185029-508.jpg
  4. https://img.freepik.com/free-vector/hand-drawn-owl-outline-illustration_23-2149277379.jpg
  5. https://img.freepik.com/free-vector/hand-drawn-fox-outline-illustration_23-2149272718.jpg
  6. https://img.freepik.com/free-vector/hand-drawn-lion-outline-illustration_23-2149285355.jpg
  7. https://img.freepik.com/free-vector/hand-drawn-penguin-outline-illustration_23-2150582038.jpg
  8. https://img.freepik.com/free-vector/animal-doodle-outline-cute-giraffe_1308-81895.jpg

- Thumbnails should be small and easy to navigate.

After selecting an image:
- Display the chosen image full-screen vertically.
- Top-left corner:
  - "Back" button: returns to image selection after confirmation dialog.
  - "Save" button: downloads the colored image.
- Top-right corner:
  - Large red circle indicating the current selected color (default is bright blue).
  - On clicking the circle, display a fullscreen palette with 24 vibrant color options arranged as small circles. After selecting a color, close the palette.

Coloring interaction:
- Detect boundaries of image areas.
- On click/tap within boundaries, fill the area with the selected color.

Q: What should the confirmation dialog say when returning to image selection?
A: Are you sure you want to go back? Any unsaved changes will be lost.

Q: What should happen when the 'Save' button is clicked?
A: Just save it in PNG format.