XP Gem Pickup Part 1

Add this game-feel effect to my 2D game: XP Gem Pickup — Magnet Swirl.

Reference scene (context only — map it onto my own characters and sizes):
A top-down 2D horde-survival arena. Art is pixel art: the hero (12×13 art pixels) is drawn at 4px (48×52px) and stands in the center; 12 small orange slimes (16×12 art pixels at 3px, 48×36px) circle him on an ellipse 170px wide-radius and 58px tall-radius, a full turn every 12s, wobbling ±5% in radius and hopping 4px. All sizes below are screen pixels at that scale — scale them to your own sprite size. Times are seconds, t = 0 is the moment the hero collects the gem. Every second: at t = −0.65 the hero fires a tiny gold #FFC24B square bolt (10px, 2-square trail) that hits one slime at t = −0.55; that slime flashes white, squashes (x 1→1.4, y 1→0.4, fading in 0.08s) and bursts into 7 orange/cream squares that fly 8→38px out and fade in 0.3s. It drops a mint XP gem (7×8 art pixels at 5px, about 35×40px, mint #5BE3B0 with a dark #1a1014 outline and a soft mint glow circle of radius 20px at 20% opacity) that hops 12px up and down in 0.15s and waits. The empty slime spot refills 3s later with a 0.25s easeOutBack pop-in. Top HUD: an XP label (3×5 pixel font, 3px cells, mint) and a 12px-tall XP bar split in quarters, mint fill with a 3px lighter top edge. Each gem adds 1/4 of the bar over 0.12s (easeOutCubic). On every 4th gem the bar is full: the whole bar flashes cream (fading over 0.6s), a gold 'LV UP!' (4px cells) pops from 40% to 120% then 100% and rises 16px above the hero for 0.8s, and the bar empties between 0.45s and 0.6s.

The effect:
The gem waits until t = −0.32, then spirals into the hero. Measure its start angle a0 and distance r0 from the hero (divide the y offset by 0.9 so the spiral is slightly flattened). …

The rest of this prompt — exact sizes, easing, colors and particle counts — and full prompts 2–6 are in the pack.