Sure! Here's an example of a simple turn-based 3D strategy game implemented as a single HTML file. The game uses JavaScript and is enclosed within `` tags:
<br><br>
<br>
<style>
canvas {
border: 1px solid black;
}
</style>
<canvas id="gameCanvas" width="400" height="400"></canvas>
Please note that this is just a basic template to give you an idea of how a turn-based 3D strategy game could be implemented in HTML and JavaScript. You will need to fill in the actual game logic and rendering based on your specific requirements. Also, keep in mind that creating a full-fledged 3D game in just one HTML file might not be practical, so consider using external JavaScript and CSS files for better organization.