first version with up movement working

Co-authored-by: Copilot <copilot@github.com>

src/game/platforms.js

@@ -0,0 +1,52 @@
+
+const SPACE_BETWEEN_PLATFORMS = 80;
+
+function createPlatform(x, y, elevation, width = 60) {
+    const platform = new Sprite();
+    platform.x = x;
+    platform.y = y;
+    platform.elevation = elevation;
+    platform.w = width;
+    platform.h = 15;
+    platform.physics = 'static';
+    platform.bounciness = 0;
+    return platform;
+}
+
+
+export function updatePlatforms(platforms, elevation, elGain) {
+    if (elGain <= 0)
+        return platforms;
+
+    let minY = height;
+    for (let i = platforms.length - 1; i >= 0; i--) {
+        const plat = platforms[i];
+        plat.y += elGain;
+        if (plat.y > height) {
+            platforms.remove(plat);
+            continue;
+        }
+        if (plat.y < minY) {
+            minY = plat.y;
+        }
+    }
+
+    // Add new platforms at the top
+    let spawnY = minY - SPACE_BETWEEN_PLATFORMS;
+    while (spawnY >= SPACE_BETWEEN_PLATFORMS) {
+        const newPlat = createPlatform(random(40, width - 40), spawnY, elevation + minY - spawnY);
+        platforms.add(newPlat);
+        spawnY -= SPACE_BETWEEN_PLATFORMS;
+    }
+    return platforms;
+}
+
+
+export function initPlatforms() {
+    let platforms = new Group();
+    updatePlatforms(platforms, 10, 10);
+
+    const basePlatform = createPlatform(width / 2, height - 10, 0, width);
+    platforms.add(basePlatform);
+    return platforms;
+}