Sure! Here's an example of a Viking board game implemented as a single HTML file using JavaScript. To make it suitable for a 9-year-old to play on a smartphone, I'll keep the game mechanics simple and use pictogram-like images as icons.
In this example, the game board is represented by a 3x3 grid using flexbox for layout. The cells represent the positions on the board that players can move to. The yellow circle in one of the cells represents an item that players can collect.
Players take turns by clicking on a cell. When a player collects an item, their item count increases. The game checks if the current player has collected all the items (in this case, just one item) and alerts the player about their victory. The game also resets the item counts to start a new game.
Please note that this is a simplified example to get you started. You can enhance the game with more features, such as randomizing the item positions, adding more items, adding dice rolls for movement, etc.