diff --git a/src/js/game-pong-context2d.js b/src/js/game-pong-context2d.js
index 8ccc812..1c43f0a 100644
--- a/src/js/game-pong-context2d.js
+++ b/src/js/game-pong-context2d.js
@@ -10,8 +10,8 @@ class PingPong_CTX2D {
   static get STATE_PLAYING() { return 1; };
   static get STATE_ENDED() { return 2; };
   static get BALL_SIZE() { return 8; };
-  static get SPEED_HUMAN() { return 180; };
-  static get SPEED_CPU() { return 210; };
+  // static get SPEED_HUMAN() { return 180; };
+  // static get SPEED_CPU() { return 210; };
 
   static get PADDLE_WIDTH() { return 10; };
   static get PADDLE_HEIGHT() { return 60; };
@@ -28,12 +28,13 @@ class PingPong_CTX2D {
   animationRequestId = 0;
   running = false;
 
-  constructor(divId, width, height, zoom = 1, showFps = false) {
-    this.createCanvas(divId, width, height, zoom);
+  constructor(divId, width, height, difficulty = 1, showFps = false) {
+    this.createCanvas(divId, width, height);
     this.canvasEl.title = "Playing: PingPong";
     this.ctx = this.canvasEl.getContext("2d");
     this.ctx.textAlign = "center";
 
+    this.difficulty = difficulty;
     this.audioCtx = new AudioContext();
     this.sounds = [];
     this.sounds[0] = new Audio('./snd/glass-knock.mp3');
@@ -70,7 +71,7 @@ class PingPong_CTX2D {
     if (typeof WTerminal === "function") {
       WTerminal.terminalAddCommand("restartgame", (t) => this.terminalRestartGame(t));
       WTerminal.terminalAddCommand("printgame", (t) => t.printVar(this, "pong"));
-      WTerminal.printLn("new PingPong: @", divId, ' ', width, 'x', height, ':', zoom, ' showFps=', showFps);
+      WTerminal.printLn("new PingPong: @", divId, ' ', width, 'x', height, ' difficulty=', difficulty, ' showFps=', showFps);
     }
 
     this.drawCanvas();
@@ -95,10 +96,33 @@ class PingPong_CTX2D {
   newRound() {
     this.countDown = 3; // seconds;
     this.gameState = PingPong_CTX2D.STATE_COUNTDOWN;
+    // set paddle speeds
+    if (this.difficulty == 0) {
+      this.speedHuman = 100;
+      this.speedCPU = 80;
+    } else if (this.difficulty == 1) {
+      this.speedHuman = 180;
+      this.speedCPU = 210;
+    } else {
+      this.speedHuman = 150 + 30 * this.difficulty;
+      this.speedCPU = 170 + 40 * this.difficulty;
+    }
+
     // randomize ball speed
-    let vx = 200 + Math.random() * 100;
-    let vy = -20 + Math.random() * 20;
-    if (Math.random() > 0.5) vx = - vx;
+    let vx = 100;
+    let vy = 0;
+    if (this.difficulty == 0) {
+      vx = 100 + Math.random() * 50;
+      vy = -10 + Math.random() * 10;
+    } else if (this.difficulty == 1) {
+      vx = 200 + Math.random() * 100;
+      vy = -20 + Math.random() * 20;
+      if (Math.random() > 0.5) vx = - vx;
+    } else {
+      vx = 200 + 100 * this.difficulty + Math.random() * 80 * this.difficulty;
+      vy = -30 + 10 * this.difficulty + Math.random() * 10 * this.difficulty;
+      if (Math.random() > 0.5) vx = - vx;
+    }
     if (Math.random() > 0.5) vy = - vy;
     // generate objects
     this.ball = new Ball(this.width / 2 - PingPong_CTX2D.BALL_SIZE / 2, this.height / 2 - PingPong_CTX2D.BALL_SIZE / 2,
@@ -235,9 +259,9 @@ class PingPong_CTX2D {
     } else if (this.gameState == PingPong_CTX2D.STATE_PLAYING) {
       //cpu actions
       if (this.ball.y + this.ball.height / 2 < this.cpu.y + this.cpu.height / 2) {
-        this.cpu.vy = -PingPong_CTX2D.SPEED_CPU;
+        this.cpu.vy = -this.speedCPU;
       } else if (this.ball.y > this.cpu.y + this.cpu.height / 2) {
-        this.cpu.vy = PingPong_CTX2D.SPEED_CPU;
+        this.cpu.vy = this.speedCPU;
       } else {
         this.cpu.vy = 0;
       }
@@ -351,11 +375,11 @@ class PingPong_CTX2D {
       return false;
     }
     if (e.key == PingPong_CTX2D.KEY_ARROW_UP || e.key == PingPong_CTX2D.KEY_W) {
-      this.human.vy = -PingPong_CTX2D.SPEED_HUMAN;
+      this.human.vy = -this.speedHuman;
       e.preventDefault();
       return false;
     } else if (e.key == PingPong_CTX2D.KEY_ARROW_DOWN || e.key == PingPong_CTX2D.KEY_S) {
-      this.human.vy = PingPong_CTX2D.SPEED_HUMAN;
+      this.human.vy = this.speedHuman;
       e.preventDefault();
       return false;
     } else if (e.key == PingPong_CTX2D.KEY_ENTER || e.key == PingPong_CTX2D.KEY_SPACEBAR) {
@@ -466,6 +490,6 @@ class Paddle extends Rectangle {
   }
 }
 
-function startPingPong(divId, width = 480, height = 320, zoom = 1, showFps = true) {
-  return new PingPong_CTX2D(divId, width, height, zoom, showFps);
+function startPingPong(divId, width = 480, height = 320, difficulty = 1, showFps = true) {
+  return new PingPong_CTX2D(divId, width, height, difficulty, showFps);
 }
diff --git a/src/js/game-tetris-context2d.js b/src/js/game-tetris-context2d.js
index 5d2a6ba..0bd53fe 100755
--- a/src/js/game-tetris-context2d.js
+++ b/src/js/game-tetris-context2d.js
@@ -5,7 +5,7 @@ class Tetris_CTX2D {
   static get DEBUG_PARENT_OBJECT() { return true; };
   static get AUTO_CONTINUE_ON_FOCUS() { return false; };
   static get SHOW_FPS_INTERVAL() { return 1000 / 4; }; // four times per second
-  static get TICK_TIME() { return 1 / 4; };
+  // static get TICK_TIME() { return 1 / 4; };
 
   static get STATE_RUNNING() { return 0; };
   static get STATE_ENDED() { return 1; };
@@ -58,11 +58,12 @@ class Tetris_CTX2D {
   running = false;
   animationRequestId = 0;
 
-  constructor(divId, width, height, zoom = 1, showFps = false) {
-    this.createCanvas(divId, width, height, zoom);
+  constructor(divId, width, height, difficulty = 1, showFps = false) {
+    this.createCanvas(divId, width, height);
     this.canvasEl.title = "Playing: Tetris";
     this.ctx = this.canvasEl.getContext("2d");
     this.ctx.textAlign = "center";
+    this.difficulty = difficulty;
 
     this.BLOCK_WIDTH = this.width / Tetris_CTX2D.GRID_COLUMS;
     this.BLOCK_HEIGHT = this.height / Tetris_CTX2D.GRID_ROWS;
@@ -103,7 +104,7 @@ class Tetris_CTX2D {
 
     if (Tetris_CTX2D.DEBUG_PARENT_OBJECT) window.game = this;
     if (typeof terminalAddCommand === "function") terminalAddCommand("restartgame", (t) => this.terminalRestartGame(t));
-    if (typeof terminalPrintLn === "function") terminalPrintLn("new Tetris_CTX2D: @", divId, ' ', width, 'x', height, ':', zoom, ' showFps=', showFps);
+    if (typeof terminalPrintLn === "function") terminalPrintLn("new Tetris_CTX2D: @", divId, ' ', width, 'x', height, ' difficulty=', difficulty, ' showFps=', showFps);
 
     this.drawCanvas();
   }
@@ -288,6 +289,12 @@ class Tetris_CTX2D {
   newGame() {
     this.gameState = Tetris_CTX2D.STATE_RUNNING;
     this.tickTime = 0;
+    this.stepTime = 1/4;
+    if(this.difficulty == 0){
+      this.stepTime = 1/2;
+    }else{
+      this.stepTime = this.stepTime/ this.difficulty;
+    }
     this.initBoard();
     this.score = 0;
     this.nextShape = this.newShape();
@@ -339,8 +346,8 @@ class Tetris_CTX2D {
     //#state switch
     if (this.gameState == Tetris_CTX2D.STATE_RUNNING) {
       this.tickTime += timeDelta;
-      if (this.tickTime >= Tetris_CTX2D.TICK_TIME) {
-        this.tickTime -= Tetris_CTX2D.TICK_TIME;
+      if (this.tickTime >= this.stepTime) {
+        this.tickTime -= this.stepTime;
         this.tick();
       }
     }
@@ -416,7 +423,7 @@ class Tetris_CTX2D {
     }
     // tickTime
     ctx.strokeStyle = '#8080B0';
-    const rotation = this.tickTime / Tetris_CTX2D.TICK_TIME * Math.PI / 2;
+    const rotation = this.tickTime / this.stepTime * Math.PI / 2;
     for (let i = 0; i < 4; i++) {
       const r = rotation + i * Math.PI / 2;
       ctx.beginPath();
@@ -498,9 +505,8 @@ class Tetris_CTX2D {
         e.preventDefault();
         return false;
       } else if (e.key == Tetris_CTX2D.KEY_ARROW_DOWN || e.key == Tetris_CTX2D.KEY_S) {
-        if (this.isValidMove(0, 1)) {
-          this.currentY++;
-        }
+        this.tick();
+        this.tickTime = 0;
         e.preventDefault();
         return false;
       } else if (e.key == Tetris_CTX2D.KEY_ARROW_LEFT || e.key == Tetris_CTX2D.KEY_A) {
@@ -555,6 +561,6 @@ class Tetris_CTX2D {
   }
 }
 
-function startTetris(divId, width = 300, height = 600, zoom = 1, showFps = true) {
-  return new Tetris_CTX2D(divId, width, height, zoom, showFps);
+function startTetris(divId, width = 300, height = 600, difficulty = 1, showFps = true) {
+  return new Tetris_CTX2D(divId, width, height, difficulty, showFps);
 }
diff --git a/src/js/games-launcher.js b/src/js/games-launcher.js
index fb903dc..6ce1a67 100644
--- a/src/js/games-launcher.js
+++ b/src/js/games-launcher.js
@@ -47,7 +47,7 @@ class GamesLauncher {
 
     this.widthEl = createElement('input', { type: 'number', id: 'width', value: '480', style: 'float: right;' });
     this.heightEl = createElement('input', { type: 'number', id: 'height', value: '320', style: 'float: right;' });
-    this.zoomEl = createElement('input', { type: 'number', id: 'zoom', value: '1', style: 'float: right;' });
+    this.difficultyEl = createElement('input', { type: 'number', id: 'difficulty', value: '1', style: 'float: right;' });
     this.showFpsEl = createElement('input', { type: 'checkbox', id: 'showFps', style: 'float: right;' });
 
     this.gameEl.appendChild(createElement('label', { for: 'width' }, 'Width: '));
@@ -56,8 +56,8 @@ class GamesLauncher {
     this.gameEl.appendChild(createElement('label', { for: 'height' }, 'Height: '));
     this.gameEl.appendChild(this.heightEl);
     this.gameEl.appendChild(createElement('br'));
-    this.gameEl.appendChild(createElement('label', { for: 'zoom' }, 'Zoom: '));
-    this.gameEl.appendChild(this.zoomEl);
+    this.gameEl.appendChild(createElement('label', { for: 'difficulty' }, 'difficulty: '));
+    this.gameEl.appendChild(this.difficultyEl);
     this.gameEl.appendChild(createElement('br'));
     this.gameEl.appendChild(createElement('label', { for: 'showFps' }, 'showFps: '));
     this.gameEl.appendChild(this.showFpsEl);
@@ -86,12 +86,12 @@ class GamesLauncher {
       case 'pong-context2d':
         this.widthEl.value = 480;
         this.heightEl.value = 320;
-        this.zoomEl.value = 1;
+        // this.difficultyEl.value = 1;
         break;
       case 'tetris-context2d':
         this.widthEl.value = 300;
         this.heightEl.value = 600;
-        this.zoomEl.value = 1;
+        // this.difficultyEl.value = 1;
         break;
     }
   }
@@ -100,17 +100,17 @@ class GamesLauncher {
     const selectedValue = this.selectGameEl.value;//this.selectGameEl.options[this.selectGameEl.selectedIndex].value;
     const width = this.widthEl.value;
     const height = this.heightEl.value;
-    const zoom = this.zoomEl.value;
+    const difficulty = this.difficultyEl.value;
     const showFps = this.showFpsEl.checked;
     switch (selectedValue) {
       case 'pong-context2d':
         this.createCloseExitGameButton();
-        this.currentGame = new PingPong_CTX2D(this.gameId, width, height, zoom, showFps);
+        this.currentGame = new PingPong_CTX2D(this.gameId, width, height, difficulty, showFps);
         this.currentGame.canvasEl.focus();
         break;
       case 'tetris-context2d':
         this.createCloseExitGameButton();
-        this.currentGame = new Tetris_CTX2D(this.gameId, width, height, zoom, showFps);
+        this.currentGame = new Tetris_CTX2D(this.gameId, width, height, difficulty, showFps);
         this.currentGame.canvasEl.focus();
         break;
       default: