Explore the 'App design' section of the Streamlit documentation. Identify the key principles for good app design, find out how to customize the app's appearance (e.g., wide mode, sidebar position), and locate information on how to add a theme. Additionally, find out what is recommended for structuring a large Streamlit app.
Navigate to 'docs.streamlit.io'. Click on 'Develop' (ID 53). Click on 'Concepts' (ID 61). Click on 'App design' (ID 108). Identify the key principles or best practices for Streamlit app design. Locate information on how to customize the app's appearance, specifically wide mode and sidebar position. Find details about adding a theme to the Streamlit app. Look for recommendations on structuring a large Streamlit application. Synthesize all gathered information into a concise answer.
The agent successfully navigates to the 'App design' page. The agent identifies and lists at least two key principles for good app design (e.g., 'Keep it simple', 'Use whitespace effectively', 'Guide your users'). The agent explains how to enable wide mode (e.g., `st.set_page_config(layout='wide')`) and how to control sidebar position (e.g., `initial_sidebar_state='expanded'` or `collapsed`). The agent states how to add a theme (e.g., through `config.toml` or `st.set_page_config`). The agent provides recommendations for structuring large Streamlit apps (e.g., organizing code into functions, modules, or using multipage app structures).