Introduce a shake animation to visually indicate invalid inputs and wire it into validation/error flows. Changes: import QPoint; add animate_widget_shake(QWidget) implementation that uses QPropertyAnimation on widget.pos with keyframes; call the animation when URL/path/format validations fail and replace some direct status_label updates with set_status_message_animated. Updated files: ytsage/gui/ytsage_gui_main.py and ytsage/gui/ytsage_gui_analysis.py.
Use animated show/hide for playlist widgets and harden fade animations. Replace direct setVisible signal handlers with lambdas that call set_widget_visible_animated, and add set_widget_visible_animated to route to fade-in/out. Fade methods now stop opposing animations, reuse existing QGraphicsOpacityEffect when present, preserve current opacity as start values, and set effect opacity when creating a new effect. Also catch possible RuntimeError when stopping animations and keep animation references on widgets to avoid premature GC.
Introduce smooth UI transitions by adding opacity-based animations. Import QGraphicsOpacityEffect and add animate_widget_fade_in, animate_widget_fade_out, and set_status_message_animated to cross-fade status text and fade buttons in/out. Update signal handlers and download flow to use the new animated status setter and fade methods instead of direct setText/setVisible calls. Keep animation references on widgets to avoid premature GC and remove effects after fade-out.
Moved all files from src/gui/ to ytsage/gui/ and updated import statements to use relative imports within the new package structure. This improves modularity and prepares the codebase for distribution as a proper Python package.
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