Sure, here's a simple game implemented as a single HTML file using JavaScript. It features a square that you can press to increase your score. The game is designed for smartphone operation and uses pictograms.
⬜️
Score: 0
To play the game, simply open the HTML file on your smartphone, and every time you tap or press the square, your score will increase by one. The current score is displayed below the square. The square is represented by a white square emoticon (⬜️).