diff --git a/index.js b/index.js
index 1484b99..22d3084 100644
--- a/index.js
+++ b/index.js
@@ -33,7 +33,8 @@ window.onload = function () {
     pace: 1,
     wave: 0,
     waveTimer: 0,
-    tower: 'simple'
+    tower: 'simple',
+    sellRatio: .8
   }
 
   /**
@@ -533,6 +534,16 @@ window.onload = function () {
     }, tower))
   }
 
+  function sellTower (x, y) {
+    var tower = getTowerAt(x, y)
+    if(tower) {
+      Game.money += tower.cost * Game.sellRatio
+      return Game.towers.splice(Game.towers.indexOf(tower), 1)
+    }else{
+      return null
+    }
+  }
+
   function update (dt) {
     fpsCount++
     fpsCount %= 20
@@ -577,7 +588,7 @@ window.onload = function () {
       let y = Math.floor(index / Maps.width)
       let x = Math.floor(index % Maps.height)
       var draw_tile = true
-
+     
       if (tile === 1) {
         ctx.fillStyle = '#fdd'
       } else if (tile === 2) {
@@ -603,28 +614,6 @@ window.onload = function () {
       let tower = Game.towers[i]
       ctx.fillStyle = tower.icon
       ctx.fillRect(tower.x * mt + 2, tower.y * mt + 2, 28, 28)
-
-      if (Game.state === 2 && Game.tower) {
-        // tower placement restriction visualization
-        for (let i = 0; i < 4; i++) {
-          let ax = tower.x
-          let ay = tower.y
-          if (i == 0) {
-            ax -= 1
-          } else if (i == 1) {
-            ax += 1
-          } else if (i == 2) {
-            ay -= 1
-          } else if (i == 3) {
-            ay += 1
-          }
-          
-          if (ax < 0 || ay < 0 || ay > Maps.height || ax > Maps.width) continue
-          if (getTileIn(Game.map.tiles, ax, ay) !== 0) continue
-          ctx.fillStyle = 'rgba(255, 0, 0, 0.45)'
-          ctx.fillRect(ax * mt, ay * mt, mt, mt)
-        }
-      }
     }
 
     for (let i in Game.enemies) {
@@ -733,6 +722,13 @@ window.onload = function () {
 
     clickBtn()
   })
+  
+  canvas.addEventListener('contextmenu', (e) => {
+    if (Game.state === 2 && mX < Maps.width && mY < Maps.height &&
+      sellTower(mX, mY)) {
+      e.preventDefault()
+    }
+  })
 
   canvas.addEventListener('mousemove', (e) => {
     if (e.changedTouches) {