fix player collision box

src/util/usePlayer.ts

@@ -1,5 +1,5 @@
 import { computed, reactive } from 'vue'
-import { RECIPROCAL } from '../level/def'
+import { RECIPROCAL, STAGE_WIDTH, STAGE_HEIGHT } from '../level/def'
 
 export interface Moveable {
   x: number, // position on x-axis (fixed for the player)
@@ -10,8 +10,8 @@ export interface Moveable {
 }
 
 const player = reactive({
-  x: 16,
-  y: 10,
+  x: (STAGE_WIDTH + 2) / 2,
+  y: (STAGE_HEIGHT + 2) / 2,
   lastDir: 0,
   vx: 0,
   vy: 1, // always falling, because of gravity