Pawn move a5 squanders Black's advantage by doing nothing to address the immediate threat. Rb1+ forces the King into the open and initiates a decisive attack, capitalizing on Black's superior position.
Promotion to Queen immediately loses. The engine's suggested check, Rf4+, forces the King to a square where further checks can be applied, prolonging the game.
3 Key Takeaways
The recurring theme in your mistakes seems to be missing tactical opportunities in favor of less impactful moves. You appear to have a good grasp of positional advantage, but need to sharpen your calculation skills to find decisive blows.
Here are three key takeaways for your next game:
Always consider forcing moves (checks, captures, threats) first: Before making any move, ask yourself, "Can I check the King, capture a piece, or threaten something important?"
Visualize several moves ahead: Don't just look at the immediate impact of your move. Try to visualize the opponent's likely response and your counter-response.
Prioritize active piece placement over pawn advancement: Pawn moves can create weaknesses. Focus on getting your pieces actively involved in the game, especially in attacking opportunities. You've got this!