Steel Keep

Cinevva's analyzer read this game's design doc and its source, then wrote the brief below. "Make your own" hands it to the game creator as your opening message, so you start from a real spec rather than a one-line idea.

Create a browser-based 2D top-down arena defense game titled "Steel Keep". Use a fixed full-screen canvas with a centered circular radar-like arena; the camera does not scroll. The visual style is dark sci-fi: nearly black navy background with a soft radial blue glow centered on the arena, thin cyan/blue concentric rings and eight radial guide lines, and a brighter cyan outer ring. Use clean geometric canvas shapes, neon cyan/blue HUD accents, and compact uppercase system-style typography.

Start on a centered translucent dark panel with a thin blue border and inset shadow. Show the large spaced uppercase title STEEL KEEP, the subtitle "A COOPERATIVE ARENA DEFENSE HOMAGE", two outlined buttons labeled START 1P and START 2P, and two control cards: P1 uses WASD to move and SPACE to fire; P2 uses ARROW keys to move and ENTER to fire. Include the instruction "Protect the core. Intercept raiders before they rip off the cargo." Touch/mobile controls should also be available: a bottom-left circular four-direction pad with a central FIRE button for player 1, and in 2-player mode a matching pad at bottom-right for player 2. Hide the menu after starting.

The objective is to protect a glowing core at the exact center of the arena. The core is drawn as a dark teal circular housing outlined in cyan with a small pulsing pale center and a soft glow. The HUD is fixed along the top: left side shows WAVE 1 and a cyan SCORE 000000; right side shows CORE 100% and 1P or 2P. The score is six-digit zero-padded. The core begins at 100%; enemies that reach the core drain it continuously, and the run ends when it reaches zero. Show a centered dark panel reading CORE LOST, the final wave and score, and a RUN IT BACK button.

Support one or two players. Player 1 is a small cyan arrow/ship and starts just below the core, slightly left of center; move with WASD and fire with Space. Player 2 is an orange/gold arrow/ship starting just below the core, slightly right of center; move with the arrow keys and fire with Enter. Players accelerate toward a movement direction and are constrained inside the circular arena. Each ship aims automatically at the nearest enemy when firing; if there is no enemy, fire in its current facing direction. Draw a short fading movement trail behind each ship. Shots are fast colored cyan/orange tracer lines emitted from the ship nose, with a brief muzzle particle burst and a short firing cooldown. Holding the fire key repeatedly fires.

Enemies spawn just outside a random side of the circular arena and travel inward toward the central core. The normal raider is a small red/pink angular wedge or arrow with a pale outline, one hit point, and a modest speed. Its orientation follows its movement. After wave 2, occasionally spawn a heavier larger raider with an orange ring/outline and three hit points; it is slower but damages the core more heavily. Enemies should have a slight sinusoidal/wobbling steering motion while homing toward the core. When close to the core, continuously reduce core health (normal raider about 3.4 per second, heavy about 5.2 per second) and add a subtle screen shake.

Bullets collide with enemies. A normal raider awards 50 points when destroyed; a heavy awards 150. Use pink/red explosion particles for normal enemies and orange particles for heavy enemies, plus small hit flashes. There is a 16% chance for a defeated enemy to drop a collectible power-up at its position. Power-ups are rotating outlined circles with a colored translucent fill and a symbol: green "+" for repair, yellow "×" for rapid fire, or coral/orange "✦" for nova. They expire after roughly 12 seconds and are collected when a player touches them. Repair restores 18 core percentage points (up to 100), rapid fire grants that player 7 seconds of faster firing, and nova destroys enemies within about 150 pixels of the pickup and awards 50 points per enemy. Show particle bursts for pickups and explosions.

The game begins at wave 1 and spawns enemies at a gradually increasing rate as the wave increases, with a minimum spawn interval. Every 28 seconds advance the wave, restore 8 core percentage points up to 100, and create a bright cyan burst around the core. There is no separate wave-clear screen; the action continues continuously. Keep all gameplay elements inside the arena except spawning enemies just beyond its perimeter. Use subtle particles, pulsing core glow, colored hit flashes, and brief camera shake to make impacts readable while retaining the restrained dark radar aesthetic. Implement responsive sizing so the arena radius is approximately 34% of the smaller viewport dimension and the HUD/menu scale on mobile.