diff --git a/index.html b/index.html
index 9b1d5b9..c2ddf5b 100644
--- a/index.html
+++ b/index.html
@@ -22,7 +22,7 @@
     <div id="table-container">
         <table id="inputs">
             <tr></tr>
-            <tr v-bind:class="{focused: focused=='sw'||focused=='sh'||focused=='sheet'}">
+            <tr v-bind:class="{focused: isFocused('sw','sh','sheet')}">
                 <td>Sheet Size:</td>
                 <td><input @focus="setFocus('sw')" @blur="resetFocus()" v-model="sw" v-bind:disabled="sheet>0"
                            type="number" min="1" step="0.1"></td>
@@ -36,7 +36,7 @@
                     </select>
                 </td>
             </tr>
-            <tr v-bind:class="{focused: focused=='m'||focused=='n'}">
+            <tr v-bind:class="{focused: isFocused('m','n')}">
                 <td>Boxes:</td>
                 <td><input @focus="setFocus('m')" @blur="resetFocus()" v-model="m" type="number" min="1" step="1"></td>
                 <td>×</td>
@@ -44,7 +44,7 @@
                 <td></td>
                 <td></td>
             </tr>
-            <tr v-bind:class="{focused: focused=='bw'||focused=='bh'}" v-if="!incomplete">
+            <tr v-bind:class="{focused: isFocused('bw','bh')}" v-if="!incomplete">
                 <td>Box size:</td>
                 <td><input @focus="setFocus('bw')" @blur="resetFocus()" id="bw" v-model="bw"
                            v-bind:disabled="(finishedH && !bw) || fbw"
@@ -56,7 +56,7 @@
                 <td><small>cm</small></td>
                 <td><span><input v-model="ratio" type="checkbox">Use ratio</span></td>
             </tr>
-            <tr v-bind:class="{focused: focused=='rw'||focused=='rh'||focused==='ratio'}" v-if="ratio && !incomplete">
+            <tr v-bind:class="{focused: isFocused('rw','rh','ratio')}" v-if="ratio && !incomplete">
                 <td>Box ratio:</td>
                 <td><input @focus="setFocus('rw')" v-model="rw" v-bind:disabled="ratioId>0" type="number" min="1"
                            step="1"></td>
@@ -70,7 +70,7 @@
                     </select>
                 </td>
             </tr>
-            <tr v-bind:class="{focused: focused=='mh'||focused=='mv'}" v-if="!incomplete">
+            <tr v-bind:class="{focused: isFocused('mh','mv')}" v-if="!incomplete">
                 <td>Box margin:</td>
                 <td><input @focus="setFocus('mh')" @blur="resetFocus()" id="mh" v-model="mh"
                            v-bind:disabled="finishedH && !mh" type="number"
@@ -82,7 +82,7 @@
                 <td><small>cm</small></td>
                 <td><span><input v-model="padding" type="checkbox">Sheet padding</span></td>
             </tr>
-            <tr v-bind:class="{focused: focused=='ph'||focused=='pv'}" v-if="padding && !incomplete">
+            <tr v-bind:class="{focused: isFocused('ph','pv')}" v-if="padding && !incomplete">
                 <td>Sheet padding:</td>
                 <td><input @focus="setFocus('ph')" @blur="resetFocus()" id="ph" v-model="ph"
                            v-bind:disabled="finishedH && !ph" type="number"
diff --git a/main.js b/main.js
index 55c0d81..1c72423 100644
--- a/main.js
+++ b/main.js
@@ -46,7 +46,11 @@ const utils = {
   }
 };
 
-const data = {
+const constants = {
+  colors:{
+    red:'#c62828',
+    black:'#424242'
+  },
   papers: [
     {title: 'A0', w: 84.1, h: 118.9},
     {title: 'A1', w: 59.4, h: 84.1},
@@ -76,7 +80,6 @@ const data = {
   ]
 };
 
-
 let app = {
   el: '#app',
   data: {
@@ -154,6 +157,9 @@ let app = {
       this.focused = name;
       this.refreshValues();
     },
+    isFocused: function(...names){
+      return names.includes(this.focused);
+    },
     refreshValues: function () {
       const self = this;
       this.finishedH = false;
@@ -252,6 +258,8 @@ let app = {
     },
     redraw: function () {
       if (this.sw && this.sh) {
+        const red = constants.colors.red;
+        const black = constants.colors.black;
         const maxWidth = 0.8 * this.$el.getBoundingClientRect().width;
         let height = this.previewMaxHeight;
         let width = height * this.sw / this.sh;
@@ -282,20 +290,20 @@ let app = {
 
         for (let x = 0; x < m + 1; x++) {
           for (let y = 0; y < n + 1; y++) {
-            ctx.strokeStyle = '#c62828';
-            if (this.focused === 'rw' || this.focused === 'rh' || this.focused === 'ratio') {
+            ctx.strokeStyle = red;
+            if (this.isFocused('rw','rh','ratio')) {
               ctx.beginPath();
               ctx.moveTo(ph + (bw + mh) * x, pv + (bh + mv) * y);
               ctx.lineTo(ph + (bw + mh) * x + bw, pv + (bh + mv) * y + bh);
               ctx.stroke();
             }
-            if (this.focused === 'ph' && (x === 0 || x === m) || this.focused === 'mh' && (!(x === 0 || x === m) || !this.padding)) {
+            if (this.isFocused('ph') && (x === 0 || x === m) || this.isFocused('mh') && (!(x === 0 || x === m) || !this.padding)) {
               ctx.beginPath();
               ctx.moveTo(ph + (bw + mh) * (x - 1) + bw, pv + (bh + mv) * y + bh / 2);
               ctx.lineTo(ph + (bw + mh) * x, pv + (bh + mv) * y + bh / 2);
               ctx.stroke();
             }
-            if (this.focused === 'pv' && (y === 0 || y === n) || this.focused === 'mv' && (!(y === 0 || y === n) || !this.padding)) {
+            if (this.isFocused('pv') && (y === 0 || y === n) || this.isFocused('mv') && (!(y === 0 || y === n) || !this.padding)) {
               ctx.beginPath();
               ctx.moveTo(ph + (bw + mh) * x + bw / 2, pv + (bh + mv) * (y - 1) + bh);
               ctx.lineTo(ph + (bw + mh) * x + bw / 2, pv + (bh + mv) * y);
@@ -303,7 +311,7 @@ let app = {
             }
 
             if (x < m && y < n) {
-              ctx.strokeStyle = (this.focused === 'bw' || this.focused === 'm' || this.focused === 'n') ? '#c62828' : '#424242';
+              ctx.strokeStyle = this.isFocused('bw','m','n') ? red : black;
               ctx.beginPath();
               ctx.moveTo(ph + (bw + mh) * x, pv + (bh + mv) * y);
               ctx.lineTo(ph + (bw + mh) * x + bw, pv + (bh + mv) * y);
@@ -311,7 +319,7 @@ let app = {
               ctx.lineTo(ph + (bw + mh) * x + bw, pv + (bh + mv) * y + bh);
               ctx.stroke();
 
-              ctx.strokeStyle = (this.focused === 'bh' || this.focused === 'm' || this.focused === 'n') ? '#c62828' : '#424242';
+              ctx.strokeStyle = this.isFocused('bh','m','n') ? red : black;
               ctx.beginPath();
               ctx.moveTo(ph + (bw + mh) * x, pv + (bh + mv) * y);
               ctx.lineTo(ph + (bw + mh) * x, pv + (bh + mv) * y + bh);
@@ -323,7 +331,7 @@ let app = {
         }
 
         ctx.lineWidth = 4;
-        ctx.strokeStyle = (this.focused === 'sw' || this.focused === 'sheet') ? '#c62828' : '#424242';
+        ctx.strokeStyle = this.isFocused('sw','sheet') ? red : black;
         ctx.beginPath();
         ctx.moveTo(1, 1);
         ctx.lineTo(width - 2, 1);
@@ -331,7 +339,7 @@ let app = {
         ctx.lineTo(width - 2, height - 2);
         ctx.stroke();
 
-        ctx.strokeStyle = (this.focused === 'sh' || this.focused === 'sheet') ? '#c62828' : '#424242';
+        ctx.strokeStyle = this.isFocused('sh','sheet') ? red : black;
         ctx.beginPath();
         ctx.moveTo(1, 1);
         ctx.lineTo(1, height - 2);
@@ -347,19 +355,19 @@ let app = {
   'mounted': function () {
     const self = this;
     this.preview = document.getElementById('preview');
-    data.papers.forEach(s => {
+    constants.papers.forEach(s => {
       self.sheets.push({
         title: `${s.title} (${s.w}×${s.h}cm)`,
         w: s.w, h: s.h
       });
     });
-    data.papers.forEach(s => {
+    constants.papers.forEach(s => {
       self.sheets.push({
         title: `${s.title} landscape (${s.h}×${s.w}cm)`,
         w: s.h, h: s.w
       });
     });
-    data.ratios.forEach(r => {
+    constants.ratios.forEach(r => {
       self.ratios.push({
         title: `${r.rw}:${r.rh}`,
         rw: r.rw,