Boss Guide (Three Archetypes)
A boss appears at the end of every stage. There are three archetypes: vanguard (mechanical mobile type), serpent (mobile type), and fortress (fortified type). They rotate according to (stage - 1) % 3: vanguard on stages 1, 4, and 7; serpent on 2, 5, and 8; fortress on 3, 6, and 9; and the same order thereafter.
Common Rules
Every archetype has three HP-based phases. Phase 1 lasts from 100% to 66% HP, phase 2 from 66% to 33%, and phase 3 below 33%. Patterns become denser and movement faster and wider with each phase. At a phase transition, all enemy bullets are cleared once and the boss becomes invulnerable for one second while the screen flashes and shakes, giving you time to reset your position.
Boss HP scales as 900 × (1 + 0.40 × (S - 1)), where S = min(stage, 8). Bullet speed and firing frequency also rise, capped at the equivalent of stage 8. See Difficulty Scaling for the formulas. Defeating a boss awards 10000 × stage number bonus points, followed by a 2.5-second explosion sequence before the next stage.
vanguard — Mechanical Mobile Type
A mechanical boss with left and right wings surrounding a central core. It follows a horizontal sine wave around the center, increasing its range and speed in later phases.
- Phase 1: Combines player-aimed 5-way fan bullets with fast shard bullets fired alternately from the side cannons. Learn the alternating timing and watch which cannon fires next to choose your escape direction.
- Phase 2: Fires repeated 16-bullet rings with shifting rotation, mixed with occasional faster aimed shots. Because the rings expand concentrically, enter a gap just after launch and hold that position for several seconds.
- Phase 3: Adds a double spiral whose ring angle shifts each time, along with fast aimed shots, while the boss moves at maximum speed. Avoid hugging the edge; a position nearer the center leaves room to move back in either direction.
serpent — Mobile Type
A long serpent-shaped boss that sweeps across the upper screen in a figure-eight Lissajous curve. Its recent path forms a trail around a prominent core. The curve becomes wider and faster in later phases, making the boss itself harder to track.
- Phase 1: Uses bursts of aimed fire and periodic 3-way fans. The boss moves quickly, but its aimed bullets travel in simple straight lines and can be avoided with lateral movement.
- Phase 2: Adds groups of two or three homing bullets to the phase 1 pattern. Their turning rate is modest and they expire after three seconds, so a broad curved movement can shake them off.
- Phase 3: Aimed shots become faster, fans grow to 5-way, and homing shots arrive more often. Prioritize wide routes that prevent homing bullets from turning with you, then use minimal lateral movement to slip past straight shots.
fortress — Fortified Type
A broad, heavy block-shaped boss with several turrets. It moves slowly from side to side at a fixed vertical position, making its movement simple.
- Phase 1: Combines bullet walls whose gap changes with every shot and fans fired alternately from the side cannons. Identify each wall's opening early and slide into it.
- Phase 2: Adds timed orb projectiles that burst near the middle of the screen. Their delay gives you time to avoid the burst point and plan a route through the wall gap.
- Phase 3: Places mines near your ship and narrows the wall gaps. Internally, however, every gap remains at least 56px wide and appears at least 80px wide, so it never closes unfairly. Stay calm and identify the opening.
General Advice
All three archetypes treat phase-transition invulnerability as a brief pause. Stop forcing attacks, scan the full screen, and choose your position for the next phase to reduce the chance of taking a hit. Bombs, used with the X key, also deal 60 damage to bosses, so keeping one in reserve is useful when a phase 3 pattern becomes difficult to read.