Rail Rush

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 playable 3D endless runner titled “Rail Rush.” Use a Three.js-like perspective camera with a dark navy night-time station scene, fog, soft shadows, and a third-person camera positioned behind and slightly above the runner, looking forward down the track. The camera should follow the player’s horizontal lane movement and remain focused on the track ahead.

Build an endless railway corridor with exactly three parallel running lanes, centered at x positions approximately -2.5, 0, and 2.5. Each lane is defined by paired gray metallic rails, with regularly spaced brown wooden sleepers crossing the whole track. Put the track on a broad dark blue-gray bed, bordered by tall dark station walls on both sides. Add repeating yellow illuminated stripe segments high along both side walls. Place curved white station lamps on both sides and occasional wooden benches along the left side, giving the environment the look of a stylized empty underground/night station. Use a low-poly/blocky aesthetic, dark blue background and fog, warm yellow accents, and directional lighting that produces visible shadows.

The player is a blocky humanoid runner standing near the camera on the center lane, facing away from the camera and running forward automatically. Use a blocky character model with the visible warm orange/tan clothing and backpack-like silhouette shown in the reference, with a sprint animation while running, an idle animation when the run ends, and a jump animation while airborne. Keep the character at the near end of the track while barriers and coins move toward the camera to simulate forward motion.

Core gameplay: when a run starts, the player automatically advances through the station. The player can switch among the three lanes and jump. Keyboard controls: Left Arrow or A moves one lane left, Right Arrow or D moves one lane right, and Up Arrow, W, or Space jumps. Clamp lane movement to the left and right lanes; smoothly interpolate the character toward the selected lane. A jump launches the player upward with an initial velocity around 10.5 and gravity around 28, allowing one jump at a time and preventing a second jump until landing. Also support mobile input: horizontal swipes change lane and upward swipes jump, and show three bottom touch buttons on narrow screens (left arrow, up arrow, right arrow).

Continuously spawn construction barriers ahead in a randomly selected one of the three lanes. The barriers should be chunky construction-road barriers, preferably using a low-poly construction barrier model; use a simple red/orange rectangular fallback if needed. They travel toward the player as the track scrolls. A collision occurs when a barrier is close to the player (roughly within 1.1 units along the track and 0.9 across) and the player is not high enough in a jump (player height below roughly 1.15). On collision, stop the run and show the game-over state. Spawn barriers initially about 58 units ahead, with their interval gradually shortening as distance increases but never becoming less than about 0.55 seconds.

Also spawn a rotating gold torus coin in a random lane about 58 units ahead every approximately 0.75 seconds. Coins move toward the player, rotate visibly, and can be collected when close in depth and horizontal lane position and within jump-height range. Collecting a coin removes it and adds 8 meters to the displayed distance. Missed barriers and coins should be removed after passing the player.

The run distance should steadily increase automatically based on movement speed, starting at speed 18 and gradually accelerating with distance up to a maximum speed of 32. Display a fixed HUD over the 3D scene: a translucent dark rounded pill at upper left reading “DIST 0” (updating to the integer distance), a matching pill at upper right reading “SPEED 1.0x” (speed divided by the initial speed, one decimal place), and centered small instructional text at the top reading “← → change lane · ↑ jump · swipe on mobile.” On desktop, hide the touch controls; on mobile, show three dark translucent rounded square buttons along the bottom center labeled ◀, ▲, and ▶.

Before a run begins, show a centered translucent dark modal card with rounded corners, the title “Rail Rush,” the text “Dash through the station and dodge the barriers.” and a yellow “Start Run” button. Starting resets distance, speed, lane, player position, obstacles, and coins. When the player hits a barrier, keep the HUD visible and show the modal game-over content with a final line such as “Distance 13m — try again” and a “Run Again” button. Pressing Enter when not running should also start a run. Match the reference’s clean minimal interface, dark navy palette, warm gold UI/accent color, and blocky stylized 3D presentation.