Desktop: move with ↑↓←→ / WASD, hold Shift to slow-draw.
Phone: swipe anywhere on the field to steer — you keep moving until you swipe again. Hold the Slow Draw button for double score (or switch to a D-pad).
Leave the edge to draw into the dark and close a loop to capture it as light.
Don't touch the boss triangle or its glowing afterimages — they reach past their zone, so even the edge isn't safe. Dodge the Sparx, and keep moving or the fuse burns.
With two bosses, split them apart: the smaller side gets captured boss-and-all, and that boss freezes.