multi step day night transition with CSS filters

src/Background.vue

@@ -8,11 +8,11 @@ import solarQuartet from './solar-quartet'
 export default {
   name: 'background',
   props: {
-    x: Number
+    x: Number,
+    time: Number
   },
   data () {
     return {
-      sunY: -50.0,
       redraw: null
     }
   },
@@ -30,11 +30,19 @@ export default {
       canvas, canvas.getContext('2d'), canvasSize, canvasSize,
       godraysCanvas, godraysCanvas.getContext('2d'), godraysSize, godraysSize,
     )
-    this.redraw(this.x, this.sunY)
+    this.refresh()
   },
-  watch: {
-    x (x) {
-      this.redraw(x, this.sunY)
+  computed: {
+    sunY () {
+      // time is between 0 and 1000
+      const p = Math.PI / 1000
+      return Math.sin(this.time * p) * -100
+    }
+  },
+  methods: {
+    refresh () {
+      this.redraw(this.x, this.sunY)
+      this.timeout = setTimeout(() => this.refresh(), 50)
     }
   }
 }

src/Field.vue

@@ -1,5 +1,5 @@
 <template>
-  <div id="field">
+  <div id="field" :class="daytimeClass">
     <input v-keep-focussed type="text"
       @keydown.up="player_velocity_y = -8"
       @keydown.down="player_velocity_y = 8"
@@ -10,19 +10,19 @@
       @keyup.right="player_velocity_x = 0"
       @keyup.left="player_velocity_x = 0"
     />
-    <mountain-background :x="128 + x / 8" />
+    <mountain-background :x="128 + x / 8" :time="time" />
     <div id="wrap" :style="{transform: `translate(${tx}px, ${ty}px)`}">
       <template v-for="row in rows">
         <div v-for="block in row" class="block" :class="[block.type]" />
       </template>
     </div>
     <div id="player" :class="[player_direction]" />
-    <div id="level-indicator">x:{{ floorX }}, y:{{ floorY }}</div>
+    <div id="level-indicator">x:{{ floorX }}, y:{{ floorY }} (@{{time}})</div>
   </div>
 </template>
 
 <script>
-import throttle from 'lodash/throttle'
+// import throttle from 'lodash/throttle'
 import Level from './level'
 import MountainBackground from './Background'
 
@@ -44,7 +44,8 @@ export default {
       player_velocity_x: 0,
       player_velocity_y: 9,
       gravity: 8.0 / 20,
-      moving: false
+      moving: false,
+      time: 600
     }
   },
   mounted () {
@@ -76,10 +77,27 @@ export default {
     floorY () { return Math.floor(this.y) },
     tx () { return (this.x - this.floorX) * -BLOCK_SIZE },
     ty () { return (this.y - this.floorY) * -BLOCK_SIZE },
-    rows () { return level.grid(this.floorX, this.floorY) }
+    rows () { return level.grid(this.floorX, this.floorY) },
+    daytimeClass () {
+      const t = this.time
+      if (t >= 900 || t < 80) return "night"
+
+      if (t >= 80 && t < 120) return "morning0"
+      if (t >= 120 && t < 150) return "morning1"
+      if (t >= 150 && t < 250) return "morning2"
+
+      if (t >= 700 && t < 800) return "evening0"
+      if (t >= 800 && t < 850) return "evening1"
+      if (t >= 850 && t < 900) return "evening2"
+
+      return "day"
+    }
   },
   methods: {
     move () {
+      // set time of day in ticks
+      this.time = (this.time + 1) % 1000
+
       const x = this.x
       const y = this.y
 
@@ -193,5 +211,15 @@ export default {
 .block.stone   { background-image: url(./assets/rock.png); }
 .block.bedrock { background-image: url(./assets/bedrock.png); }
 .block.cave    { background-color: #000; }
-.block:hover, .block.highlight { filter: brightness(1.4); }
+#field .block:hover { outline: 1px solid white; z-index: 10; }
+
+.morning0 .block, .morning0 #player { filter: saturate(50%) brightness(0.6) hue-rotate(-10deg); }
+.morning1 .block, .morning1 #player { filter: saturate(100%) brightness(0.8) hue-rotate(-20deg); }
+.morning2 .block, .morning2 #player { filter: saturate(200%) hue-rotate(-30deg); }
+
+.evening0 .block, .evening0 #player { filter: brightness(0.8) hue-rotate(-10deg); }
+.evening1 .block, .evening1 #player { filter: brightness(0.6) hue-rotate(-20deg); }
+.evening2 .block, .evening2 #player { filter: brightness(0.4) hue-rotate(-10deg) saturate(50%); }
+
+.night .block, .night #player { filter: brightness(0.3) saturate(30%); }
 </style>

src/solar-quartet.js

@@ -29,8 +29,13 @@ export default function drawFrame (canvas, ctx, width, height, grCanvas, grCtx,
   // so anything lighter will result in lots of white.
   // If you're not space-bound you can add another stop or two, maybe fade out to black,
   // but this actually looks good enough.
+
   emissionGradient.addColorStop(.1, '#0C0804') // pixels in radius 0 to 4.4 (44 * .1).
   emissionGradient.addColorStop(.2, '#060201') // everything past radius 8.8.
+  /* TODO: NIGHT
+   * emissionGradient.addColorStop(.1, '#000') // pixels in radius 0 to 4.4 (44 * .1).
+   * emissionGradient.addColorStop(.2, '#000') // everything past radius 8.8.
+   */
 
   // Now paint the gradient all over our godrays canvas.
   grCtx.fillRect(0, 0, grWidth, grHeight)
@@ -43,6 +48,10 @@ export default function drawFrame (canvas, ctx, width, height, grCanvas, grCtx,
   const skyGradient = ctx.createLinearGradient(0, 0, 0, height)
   skyGradient.addColorStop(0, '#2a3e55') // Blueish at the top.
   skyGradient.addColorStop(.7, '#8d4835') // Reddish at the bottom.
+  /* TODO: NIGHT
+   * skyGradient.addColorStop(0, '#000') // Blueish at the top.
+   * skyGradient.addColorStop(.7, '#000') // Reddish at the bottom.
+   */
   ctx.fillStyle = skyGradient
   ctx.fillRect(0, 0, width, height)
 
@@ -60,6 +69,9 @@ export default function drawFrame (canvas, ctx, width, height, grCanvas, grCtx,
     // Set the main canvas fillStyle to a shade of brown with variable lightness
     // (darker at the front)
     ctx.fillStyle = `hsl(7, 23%, ${23-i*6}%)`;
+    /* TODO: NIGHT
+     * ctx.fillStyle = `hsl(5, 23%, ${4-i}%)`;
+     */
 
     // For each column in our canvas...
     for(let x = width; x--;) {