Fixed bugs and annoyances

Fixed issues mostly related to the new things in the previous build:

• Added a small menu indicator when playing using mouse or touch controls
• Fixed slightly imprecise mouse and touch position detection
• Fixed achievements not saving on the browser
• Fixed letterboxing color being white instead of black on the browser
• Fixed keyboard focus not being regained on click on the browser
• Fixed hitting Esc in the title screen confusingly closing the game
• Made the browser version stop audio and pause the game when the page isn't active

Special thanks to my patron redsh for reporting the vast majority of these!