feat(frontend): pure canvas draw functions (ship + flame + target + layout)

Frontend/src/render.ts

@@ -0,0 +1,116 @@
+import type { StateFrame } from './protocol';
+
+/** Ship as a filled triangle, drawn at (x,y) rotated by angle. Size in canvas px. */
+export function drawShip(
+  ctx: CanvasRenderingContext2D,
+  worldX: number,
+  worldY: number,
+  angle: number,
+  engine: number,
+  scale: number,
+  offsetX: number,
+  offsetY: number,
+) {
+  const px = offsetX + worldX * scale;
+  const py = offsetY + worldY * scale;
+  const size = scale * 0.04;
+
+  ctx.save();
+  ctx.translate(px, py);
+  ctx.rotate(angle);
+
+  // Body: triangle pointing up (angle=0 → up).
+  ctx.fillStyle = '#eee';
+  ctx.beginPath();
+  ctx.moveTo(0, -size);
+  ctx.lineTo(size * 0.7, size * 0.6);
+  ctx.lineTo(-size * 0.7, size * 0.6);
+  ctx.closePath();
+  ctx.fill();
+
+  // Flame if an engine is firing.
+  if (engine !== 0) {
+    ctx.fillStyle = '#ff9d3d';
+    ctx.beginPath();
+    if (engine === 2) {
+      // Main engine: flame under the ship.
+      const flame = size * 0.9 + Math.random() * size * 0.4;
+      ctx.moveTo(-size * 0.4, size * 0.6);
+      ctx.lineTo(size * 0.4, size * 0.6);
+      ctx.lineTo(0, size * 0.6 + flame);
+    } else if (engine === 1) {
+      // Left thruster: flame on right side of body.
+      ctx.moveTo(size * 0.7, -size * 0.2);
+      ctx.lineTo(size * 0.7, size * 0.2);
+      ctx.lineTo(size * 1.3, 0);
+    } else if (engine === 3) {
+      // Right thruster: flame on left side of body.
+      ctx.moveTo(-size * 0.7, -size * 0.2);
+      ctx.lineTo(-size * 0.7, size * 0.2);
+      ctx.lineTo(-size * 1.3, 0);
+    }
+    ctx.closePath();
+    ctx.fill();
+  }
+
+  ctx.restore();
+}
+
+/** Draw a crosshair at the target world position. */
+export function drawTarget(
+  ctx: CanvasRenderingContext2D,
+  worldX: number,
+  worldY: number,
+  scale: number,
+  offsetX: number,
+  offsetY: number,
+) {
+  const px = offsetX + worldX * scale;
+  const py = offsetY + worldY * scale;
+  const r = 8;
+
+  ctx.strokeStyle = '#5cf';
+  ctx.lineWidth = 1.5;
+  ctx.beginPath();
+  ctx.arc(px, py, r, 0, Math.PI * 2);
+  ctx.stroke();
+
+  ctx.beginPath();
+  ctx.moveTo(px - r * 1.5, py);
+  ctx.lineTo(px + r * 1.5, py);
+  ctx.moveTo(px, py - r * 1.5);
+  ctx.lineTo(px, py + r * 1.5);
+  ctx.stroke();
+}
+
+/** Layout: fit the 1×1 world into the canvas with black letterbox bars. */
+export function layout(canvas: HTMLCanvasElement) {
+  const scale = Math.min(canvas.width, canvas.height);
+  const offsetX = (canvas.width - scale) / 2;
+  const offsetY = (canvas.height - scale) / 2;
+  return { scale, offsetX, offsetY };
+}
+
+/** Render one frame: clear + world background + target + ship. */
+export function renderFrame(
+  canvas: HTMLCanvasElement,
+  state: StateFrame | null,
+) {
+  const ctx = canvas.getContext('2d');
+  if (!ctx) return;
+
+  // Clear
+  ctx.fillStyle = '#000';
+  ctx.fillRect(0, 0, canvas.width, canvas.height);
+
+  const { scale, offsetX, offsetY } = layout(canvas);
+
+  // World background (subtle dark band so the play area is visible).
+  ctx.fillStyle = '#0a0a12';
+  ctx.fillRect(offsetX, offsetY, scale, scale);
+
+  if (!state) return;
+
+  drawTarget(ctx, state.target[0], state.target[1], scale, offsetX, offsetY);
+  drawShip(ctx, state.x, state.y, state.angle, state.engine, scale, offsetX, offsetY);
+}