🎉 Huge update, added Python virtualenv, updated dependencies...

app/index.py

@@ -3,7 +3,7 @@ from icalendar import Calendar, Alarm
 from flask_wtf import FlaskForm
 from flask_wtf.file import FileField, FileRequired
 from wtforms import IntegerField, SubmitField
-from wtforms.widgets.html5 import NumberInput
+from wtforms.widgets import NumberInput
 import tempfile
 
 index = Blueprint('index', __name__, template_folder='templates')
@@ -41,7 +41,7 @@ def addreminder():
     new_ics = tempfile.TemporaryFile()
     new_ics.write(calendar.to_ical())
     new_ics.seek(0)
-    new_filename = file.filename.rstrip('.ics')+'_with_reminders'+'.ics'
+    new_filename = file.filename.rstrip('.ics') + '_with_reminders' + '.ics'
     return send_file(new_ics, as_attachment=True,
                      attachment_filename=new_filename)
 

app/static/css/style.css

@@ -0,0 +1,153 @@
+body {
+  background-color: #EEEEEE;
+  font-family: sans-serif;
+  text-align: center;
+  margin: 0px;
+}
+
+main {
+  padding: 12px;
+}
+
+h1 {
+  font-size: 1.25em;
+}
+
+label {
+  text-align: left;
+}
+
+ol {
+  text-align: left;
+}
+
+a:link,
+a:visited {
+  text-decoration: none;
+  color: #0066cc;
+}
+
+a:hover,
+a:active {
+  text-decoration: underline;
+  color: #0066cc;
+}
+
+div.form {
+  width: 420px;
+  margin: 0 auto;
+}
+
+div.form-group {
+  display: flex;
+  justify-content: space-between;
+  margin-bottom: 24px;
+}
+
+div.form label {
+  font-size: 18px;
+}
+
+div.form input[type="number"] {
+  width: 80px;
+}
+
+footer {
+  width: 100vw;
+  position: absolute;
+  bottom: 0px;
+  padding: 10px 0px;
+}
+
+input[type="submit"] {
+  width: 150px;
+  color: white;
+  background-color: #0066cc;
+  padding: 14px 20px;
+  margin: 18px;
+  border: none;
+  border-radius: 4px;
+  cursor: pointer;
+  font-weight: bold;
+  font-size: 18px;
+}
+
+input[type="submit"]:hover {
+  background-color: #0044aa;
+}
+
+.file {
+  position: relative;
+  display: inline-block;
+  cursor: pointer;
+  height: 2.5rem;
+  width: 100%;
+  margin-bottom: 16px;
+}
+
+.file input {
+  min-width: 14rem;
+  margin: 0;
+  filter: alpha(opacity=0);
+  opacity: 0;
+}
+.file-custom::before {
+  position: absolute;
+  top: -.075rem;
+  right: -.075rem;
+  bottom: -.075rem;
+  z-index: 6;
+  display: block;
+  content: "Browse";
+  height: 2.5rem;
+  padding: .5rem 1rem;
+  line-height: 1.5;
+  color: #555;
+  background-color: #eee;
+  border: .075rem solid #ddd;
+  border-radius: 0 .25rem .25rem 0;
+}
+
+.file-custom {
+  position: absolute;
+  top: 0;
+  right: 0;
+  left: 0;
+  z-index: 5;
+  height: 2.5rem;
+  padding: .5rem 1rem;
+  line-height: 1.5;
+  color: #555;
+  background-color: #fff;
+  border: .075rem solid #ddd;
+  border-radius: .25rem;
+  box-shadow: inset 0 .2rem .4rem rgba(0,0,0,.05);
+  -webkit-user-select: none;
+  -moz-user-select: none;
+  -ms-user-select: none;
+  user-select: none;
+}
+
+*, ::before, ::after {
+  -webkit-box-sizing: border-box;
+  -moz-box-sizing: border-box;
+  box-sizing: border-box;
+}
+.file-custom::after {
+  content: attr(data-content);
+}
+
+div.error {
+  color: #721c24;
+  background-color: #f8d7da;
+  padding: .75rem 1.25rem;
+  border: 1px solid #f5c6cb;
+  border-radius: .25rem;
+}
+
+@media all and (max-width: 500px) {
+  div.form {
+    width: 100%;
+    margin: 0 auto;
+  }
+}

app/static/js/reminder.js

@@ -0,0 +1,6 @@
+document.addEventListener("DOMContentLoaded", function(event) { 
+  document.getElementById('icsfile').addEventListener("change", function(e){
+    var filename = this.value.replace(/^.*[\\\/]/, '');
+    document.getElementById('filename').setAttribute('data-content', filename);
+  });
+});