[game] Save and restore actors

game/main.ts

@@ -2,7 +2,7 @@ import { cls, print } from "./graphics";
 import { since_start } from "./time";
 import { new_v2 } from "./vector";
 import { load_world, World, Level, draw_level } from "./level";
-import { Actor, Robo } from "./actor";
+import { Actor, Robo, ActorSnapshot, actor_from_snapshot } from "./actor";
 
 /// A nice looping frame counter.
 let clock = 0;
@@ -34,7 +34,7 @@ function load_assets() {
   });
 }
 
-const actors: Actor[] = [];
+let actors: Actor[] = [];
 
 // TODO: Build a system whereby the signatures of the fundamental functions can be checked.
 
@@ -44,11 +44,24 @@ export function init() {
   actors.push(new Robo(new_v2(10, 10)));
 }
 
-export function suspend() {
-  return { clock };
+interface Snapshot {
+  clock: number;
+  actors: ActorSnapshot[];
 }
 
-export function resume() {}
+export function suspend(): Snapshot {
+  return {
+    clock,
+    actors: actors.map((a) => a.snapshot()),
+  };
+}
+
+export function resume(snapshot: Snapshot | undefined) {
+  if (snapshot) {
+    clock = snapshot.clock || 0;
+    actors = snapshot.actors.map((a) => actor_from_snapshot(a));
+  }
+}
 
 export function update() {
   clock = (clock + 1) % 20160;