enhance delete-session functionality to optionally keep trial clicks

replace brand logo with single image; update styles for improved responsiveness

added logos

add brand logo to welcome screen; update styles for improved aesthetics

refactor welcome screen; update background handling and styling

update style.css; reduce background opacity for welcome screen

update index.html; add background element to welcome screen

update style.css; adjust layout and styling for improved readability and user experience

refactor game finish logic and UI feedback; remove final score display and update input prompt

add initial game implementation with HTML, CSS, and JavaScript