Space Blaster Game: Diving Aliens, Bosses and Power-Ups

Space Blaster is a vertical arcade shooter in the style of Galaga: alien formations fly onto the screen along curved paths, sway in place, and break off one by one to dive-bomb your ship. This snippet builds the complete game on one HTML5 <canvas> with no libraries and no image files. It plays with the arrow keys or A and D and Space, with on-screen buttons, or by dragging a finger on the game, which moves the ship under your finger and fires automatically.

Formations that fly in, sway and dive

Every alien has a slot in a formation whose centre slowly drifts from side to side. A new wave starts with each alien following a quadratic Bézier curve from off-screen to its slot, staggered by a few hundredths of a second, so the formation streams in. Once in place, aliens fire now and then (shooters aim at you, tanks fire a three-way spread) and, a few at a time, break into a dive: a curve that starts at the alien, swings sideways and ends just past your ship's position below the screen. A diving alien that misses you reappears at the top and drops back into its slot. Hitting a diver is worth double, and the number of simultaneous divers, the dive rate and the fire rate all grow with the wave.

Three alien types and a mothership

Green grunts take one hit, purple shooters two and orange tanks four; each is pixel art with two animation frames, pre-rendered into small off-screen canvases (plus a white copy for the hit flash) so drawing dozens of them costs only a drawImage each. Every fifth wave is a mothership boss with a health bar: it sweeps across the top and cycles through a rotating ring of bullets, aimed three-shot bursts, and launching kamikaze grunts. Destroying it scores 1000 plus 100 per wave and drops two power-ups.

Power-ups, combos and game feel

Destroyed aliens sometimes drop a capsule: double shot, a three-way spread, rapid fire, a shield that absorbs one hit, or a rare extra life. Weapons last ten seconds, shown as timer bars along the bottom. Kills in quick succession build a combo, and every five raise the score multiplier, up to x4. Explosions combine additive particles, an expanding shockwave ring, screen shake and a filtered-noise boom from the Web Audio API; the background is a three-layer parallax starfield over a slowly scrolling nebula, and clearing a wave triggers a hyperspace streak. The ship banks as it moves, has a flickering engine flame, and blinks while it is invulnerable after a hit.

Fair and readable

The ship's hitbox is a 9-pixel circle, smaller than the drawing, and enemy bullets are bright glowing orbs so they read clearly against the stars. Losing a life clears the enemy bullets and gives two seconds of invulnerability. The game pauses on P, Escape, the pause button or a tab switch, sound can be muted, and the best score is saved in localStorage.