Build a single-file HTML shooting game called "Acorn Squad": a cartoon squirrel defends its oak tree by throwing acorns at waves of enemies (beetles, crows and a boss raccoon). Move with arrow keys or WASD, aim with the mouse and click (or hold Space) to throw; on phones use a virtual joystick and a fire button. Acorns fly in an arc and bounce once. Draw everything in code with canvas (no external images), with hit flashes, small particle bursts and screen shake. Add waves that get harder, a health bar, a power-up that throws three acorns at once, a score with a best score saved in localStorage, and a game-over screen with a restart button. Make it feel good on both desktop and phone.