As an AI language model, I can provide you with a simple example of an Undertale-inspired game implemented as a single HTML file using JavaScript. However, please note that creating a fully functional Undertale game would require much more complex coding and assets, which goes beyond the scope of a single response. Here's a basic starting point:
This simple game randomly shows one of three pictogram options, and the player needs to click on the displayed pictogram to win. If the clicked pictogram matches the target option, a "You win!" message is displayed; otherwise, a "You lose!" message is shown. The game then restarts automatically. Please note that actual smartphone gestures and more complex gameplay mechanics would require additional coding.