Implement rewind, add a key for it, and suggest keys in general

index.html

@@ -56,6 +56,7 @@
             <h1 class="-top"></h1>
             <div class="-middle"></div>
             <p class="-bottom"></p>
+            <p class="-keyhint"></p>
         </div>
         <div class="message"></div>
         <div class="chips">

js/game.js

@@ -745,6 +745,7 @@ export class Level {
         if (actor.cell === goal_cell)
             return;
 
+        // TODO undo this stuff?
         actor.previous_cell = actor.cell;
         actor.animation_speed = speed;
         actor.animation_progress = 0;

js/main.js

@@ -268,6 +268,12 @@ class Player extends PrimaryView {
             this._redraw();
             ev.target.blur();
         });
+        this.rewind_button = this.root.querySelector('.controls .control-rewind');
+        this.rewind_button.addEventListener('click', ev => {
+            if (this.level.undo_stack.length > 0) {
+                this.state = 'rewinding';
+            }
+        });
         // Demo playback
         this.root.querySelector('.demo-controls .demo-play').addEventListener('click', ev => {
             if (this.state === 'playing' || this.state === 'paused' || this.state === 'rewinding') {
@@ -339,6 +345,14 @@ class Player extends PrimaryView {
                 ev.preventDefault();
             }
 
+            if (ev.key === 'z') {
+                if (this.level.undo_stack.length > 0 &&
+                    (this.state === 'stopped' || this.state === 'playing' || this.state === 'paused'))
+                {
+                    this.set_state('rewinding');
+                }
+            }
+
             if (this.key_mapping[ev.key]) {
                 this.current_keys.add(ev.key);
                 ev.stopPropagation();
@@ -350,6 +364,12 @@ class Player extends PrimaryView {
             }
         });
         key_target.addEventListener('keyup', ev => {
+            if (ev.key === 'z') {
+                if (this.state === 'rewinding') {
+                    this.set_state('playing');
+                }
+            }
+
             if (this.key_mapping[ev.key]) {
                 this.current_keys.delete(ev.key);
                 ev.stopPropagation();
@@ -357,6 +377,15 @@ class Player extends PrimaryView {
             }
         });
 
+        // When we lose focus, act as though every key was released, and pause the game
+        window.addEventListener('blur', ev => {
+            this.current_keys.clear();
+
+            if (this.state === 'playing' || this.state === 'rewinding') {
+                this.set_state('paused');
+            }
+        });
+
         // Populate input debugger
         this.input_el = this.root.querySelector('.input');
         this.input_action_elements = {};
@@ -366,13 +395,6 @@ class Player extends PrimaryView {
             this.input_action_elements[action] = el;
         }
 
-        // Auto pause when we lose focus
-        window.addEventListener('blur', ev => {
-            if (this.state === 'playing' || this.state === 'rewinding') {
-                this.set_state('paused');
-            }
-        });
-
         this._advance_bound = this.advance.bind(this);
         this._redraw_bound = this.redraw.bind(this);
         // Used to determine where within a tic we are, for animation purposes
@@ -554,7 +576,22 @@ class Player extends PrimaryView {
         }
 
         this.last_advance = performance.now();
-        this.advance_by(1);
+        if (this.state === 'playing') {
+            this.advance_by(1);
+        }
+        else if (this.state === 'rewinding') {
+            if (this.level.undo_stack.length === 0) {
+                // TODO detect if we hit the start of the level (rather than just running the undo
+                // buffer dry) and change to 'waiting' instead
+                // TODO pausing seems rude actually, it should just hover in-place?
+                this._advance_handle = null;
+                this.set_state('paused');
+            }
+            else {
+                // Rewind by undoing one tic every tic
+                this.level.undo();
+            }
+        }
         this._advance_handle = window.setTimeout(this._advance_bound, 1000 / TICS_PER_SECOND);
     }
 
@@ -566,6 +603,9 @@ class Player extends PrimaryView {
         // TODO i'm not sure it'll be right when rewinding either
         // TODO or if the game's speed changes.  wow!
         this.tic_offset = Math.min(0.9999, (performance.now() - this.last_advance) / 1000 / (1 / TICS_PER_SECOND));
+        if (this.state === 'rewinding') {
+            this.tic_offset = 1 - this.tic_offset;
+        }
 
         this._redraw();
 
@@ -637,7 +677,7 @@ class Player extends PrimaryView {
         if (this.state === 'paused') {
             this.set_state('playing');
         }
-        else if (this.state === 'playing') {
+        else if (this.state === 'playing' || this.state === 'rewinding') {
             this.set_state('paused');
         }
     }
@@ -653,6 +693,7 @@ class Player extends PrimaryView {
         let overlay_top = '';
         let overlay_middle = null;
         let overlay_bottom = '';
+        let overlay_keyhint = '';
         if (this.state === 'waiting') {
             overlay_reason = 'waiting';
             overlay_middle = "Ready!";
@@ -660,6 +701,7 @@ class Player extends PrimaryView {
         else if (this.state === 'paused') {
             overlay_reason = 'paused';
             overlay_bottom = "/// paused ///";
+            overlay_keyhint = "press P to resume";
         }
         else if (this.state === 'stopped') {
             if (this.level.state === 'failure') {
@@ -667,6 +709,7 @@ class Player extends PrimaryView {
                 overlay_top = "whoops";
                 let obits = OBITUARIES[this.level.fail_reason] ?? OBITUARIES['generic'];
                 overlay_bottom = random_choice(obits);
+                overlay_keyhint = "press space to try again, or Z to rewind";
             }
             else {
                 overlay_reason = 'success';
@@ -706,7 +749,7 @@ class Player extends PrimaryView {
                         "alphanumeric!", "nice dynamic typing!", 
                     ]);
                 }
-                overlay_bottom = "press spacebar to continue";
+                overlay_keyhint = "press space to move on";
 
                 overlay_middle = mk('dl.score-chart',
                     mk('dt', "base score"),
@@ -727,12 +770,22 @@ class Player extends PrimaryView {
         this.overlay_message_el.setAttribute('data-reason', overlay_reason);
         this.overlay_message_el.querySelector('.-top').textContent = overlay_top;
         this.overlay_message_el.querySelector('.-bottom').textContent = overlay_bottom;
+        this.overlay_message_el.querySelector('.-keyhint').textContent = overlay_keyhint;
         let middle = this.overlay_message_el.querySelector('.-middle');
         middle.textContent = '';
         if (overlay_middle) {
             middle.append(overlay_middle);
         }
 
+        // Ask the renderer to apply a rewind effect only when rewinding, or when paused from
+        // rewinding
+        if (this.state === 'rewinding') {
+            this.renderer.use_rewind_effect = true;
+        }
+        else if (this.state !== 'paused') {
+            this.renderer.use_rewind_effect = false;
+        }
+
         // The advance and redraw methods run in a loop, but they cancel
         // themselves if the game isn't running, so restart them here
         if (this.state === 'playing' || this.state === 'rewinding') {

js/renderer-canvas.js

@@ -25,6 +25,7 @@ export class CanvasRenderer {
         this.ctx = this.canvas.getContext('2d');
         this.viewport_x = 0;
         this.viewport_y = 0;
+        this.use_rewind_effect = false;
     }
 
     set_level(level) {
@@ -129,6 +130,24 @@ export class CanvasRenderer {
                 }
             }
         }
+
+        if (this.use_rewind_effect) {
+            this.draw_rewind_effect(tic);
+        }
+    }
+
+    draw_rewind_effect(tic) {
+        // Shift several rows over
+        let rewind_start = 1 - tic / 20 % 1;
+        for (let chunk = 0; chunk < 4; chunk++) {
+            let y = Math.floor(this.canvas.height * (chunk + rewind_start) / 4);
+            for (let dy = 1; dy < 5; dy++) {
+                this.ctx.drawImage(
+                    this.canvas,
+                    0, y + dy, this.canvas.width, 1,
+                    -dy * dy, y + dy, this.canvas.width, 1);
+            }
+        }
     }
 
     create_tile_type_canvas(name) {

style.css

@@ -328,13 +328,13 @@ body[data-mode=player] #editor-play {
     place-self: stretch;
 
     display: grid;
-    grid-template-rows: 1fr 3fr 1fr;
+    grid-template-rows: 2fr 6fr 2fr 1fr;
     justify-content: center;
     align-items: center;
 
     z-index: 1;
     font-size: calc(0.5 * var(--tile-width) * var(--scale));
-    padding: 6.25%;
+    padding: 2%;
     background: #0009;
     color: white;
     text-align: center;
@@ -350,6 +350,11 @@ body[data-mode=player] #editor-play {
 }
 #player .overlay-message .-bottom {
 }
+#player .overlay-message .-keyhint {
+    align-self: end;
+    font-size: 0.5em;
+    color: #c0c0c0;
+}
 #player .overlay-message[data-reason=""] {
     display: none;
 }