diff --git a/.gitignore b/.gitignore
index 34613a1..e32205a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -64,3 +64,7 @@ target/
 Thumbs.db
 build/*
 dist
+
+# Database
+*.db
+*.sqlite
diff --git a/README.md b/README.md
index 6b8c84c..f739e58 100644
--- a/README.md
+++ b/README.md
@@ -25,12 +25,12 @@ found [on my site](http://martinfitzpatrick.name/tag/pyqt).
 1. [Post-it Notes](notes/) - "Brown Note" (QtDesigner)
 1. [Paint](paint/) - "Piecasso" (QtDesigner)
 1. [Unzip](unzip/) - "7Pez" (QtDesigner)
-1. [Translator](translate/) - "Translataar" (QtDesigner)
+1. [Translator](translate/) - "Translataarrr" (QtDesigner)
 1. [Weather](weather/) - "Raindar" (QtDesigner)
 
 ## In progress
 
-1. Currency converter (QtDesigner, PyQtGraph)
+1. Currency converter - "Doughnut" (PyQtGraph)
 1. Solitaire - "Ronery"
 
 # License
diff --git a/currency/currency.py b/currency/currency.py
new file mode 100644
index 0000000..cd301e5
--- /dev/null
+++ b/currency/currency.py
@@ -0,0 +1,346 @@
+from PyQt5.QtGui import *
+from PyQt5.QtWidgets import *
+from PyQt5.QtCore import *
+
+import pyqtgraph as pg
+import requests
+import requests_cache
+
+
+from collections import defaultdict
+from datetime import datetime, timedelta, date
+from itertools import cycle
+import sys
+import time
+import traceback
+
+requests_cache.install_cache('fixerio_cache')
+
+# Base currency is used to retrieve rates from fixer.io.
+# If we change currency we re-request, though it would
+# be possible to calculate any rates *through* the base.
+DEFAULT_BASE_CURRENCY = 'EUR'
+DEFAULT_DISPLAY_CURRENCIES = ['CAD','CYP','AUD','USD', 'EUR', 'GBP', 'NZD', 'SGD']
+HISTORIC_DAYS_N = 180
+
+# Colour sets.
+BREWER12PAIRED = cycle(['#a6cee3', '#1f78b4', '#b2df8a', '#33a02c', '#fb9a99', '#e31a1c', '#fdbf6f', '#ff7f00',
+                  '#cab2d6', '#6a3d9a', '#ffff99', '#b15928' ])
+
+# Base PyQtGraph configuration
+pg.setConfigOption('background', 'w')
+pg.setConfigOption('foreground', 'k')
+
+
+# Build progressive request order, for filling up data
+# Uses an depth-first search pattern, filling more recent data
+# to a higher resolution more quickly with a
+DATE_REQUEST_OFFSETS = [0]
+current = [(0, HISTORIC_DAYS_N)]
+while current:
+    a, b = current.pop(0)
+    n = (a + b) // 2
+    DATE_REQUEST_OFFSETS.append(n)
+
+    if abs(a - n) > 1:
+        current.insert(0, (a, n))
+
+    if abs(b - n) > 1:
+        current.append((b, n))
+
+
+
+class WorkerSignals(QObject):
+    '''
+    Defines the signals available from a running worker thread.
+    '''
+    finished = pyqtSignal()
+    error = pyqtSignal(tuple)
+    progress = pyqtSignal(int)
+    data = pyqtSignal(int, dict)
+    cancel = pyqtSignal()
+
+
+class UpdateWorker(QRunnable):
+    '''
+    Worker thread for unzipping.
+    '''
+    signals = WorkerSignals()
+    is_interrupted = False
+
+    def __init__(self, base_currency):
+        super(UpdateWorker, self).__init__()
+        self.base_currency = base_currency
+        self.signals.cancel.connect(self.cancel)
+
+    @pyqtSlot()
+    def run(self):
+        try:
+            today = date.today()
+            total_requests = len(DATE_REQUEST_OFFSETS)
+
+            for n, offset in enumerate(DATE_REQUEST_OFFSETS, 1):
+                when = today - timedelta(days=offset)
+                url = 'http://api.fixer.io/{}'.format(when.isoformat())
+                r = requests.get(url, params={'base': self.base_currency})
+                r.raise_for_status()
+                data = r.json()
+                rates = data['rates']
+                rates[self.base_currency] = 1.0
+
+                self.signals.data.emit(offset ,rates)
+                self.signals.progress.emit(int(100 * n / total_requests))
+
+                if not r.from_cache:
+                    time.sleep(1)  # Don't be rude.
+
+                if self.is_interrupted:
+                    break
+
+
+        except Exception as e:
+            print(e)
+            exctype, value = sys.exc_info()[:2]
+            self.signals.error.emit((exctype, value, traceback.format_exc()))
+            return
+
+        self.signals.finished.emit()
+
+    def cancel(self):
+        self.is_interrupted = True
+
+
+
+class MainWindow(QMainWindow):
+
+    def __init__(self, *args, **kwargs):
+        super(MainWindow, self).__init__(*args, **kwargs)
+
+        layout = QHBoxLayout()
+
+        self.ax = pg.PlotWidget()
+        self.ax.showGrid(True, True)
+
+        self.line = pg.InfiniteLine(
+            pos=-20,
+            pen=pg.mkPen('k', width=3),
+            movable=False  # We have our own code to handle dragless moving.
+        )
+
+        self.ax.addItem(self.line)
+        self.ax.setLimits(xMin=-HISTORIC_DAYS_N + 1, xMax=0)
+        self.ax.getPlotItem().scene().sigMouseMoved.connect(self.mouse_move_handler)
+
+        self.base_currency = DEFAULT_BASE_CURRENCY
+
+        # Store a reference to lines on the plot, and items in our
+        # data viewer we can update rather than redraw.
+        self._data_lines = dict()
+        self._data_items = dict()
+        self._data_colors = dict()
+        self._data_visible = DEFAULT_DISPLAY_CURRENCIES
+
+        self._last_updated = None
+
+        self.listView = QTableView()
+        self.model = QStandardItemModel()
+        self.model.setHorizontalHeaderLabels(["Currency", "Rate"])
+        self.model.itemChanged.connect(self.check_check_state)
+
+        self.listView.setModel(self.model)
+
+        self.threadpool = QThreadPool()
+        self.worker = False
+
+        layout.addWidget(self.ax)
+        layout.addWidget(self.listView)
+
+        widget = QWidget()
+        widget.setLayout(layout)
+        self.setCentralWidget(widget)
+        self.listView.setFixedSize(226, 400)
+        self.setFixedSize(650, 400)
+
+        toolbar = QToolBar("Main")
+        self.addToolBar(toolbar)
+        self.currencyList = QComboBox()
+
+        toolbar.addWidget(self.currencyList)
+        self.update_currency_list(DEFAULT_DISPLAY_CURRENCIES)
+        self.currencyList.setCurrentText(self.base_currency)
+        self.currencyList.currentTextChanged.connect(self.change_base_currency)
+
+        self.progress = QProgressBar()
+        self.progress.setRange(0, 100)
+        toolbar.addWidget(self.progress)
+
+        self.refresh_historic_rates()
+        self.setWindowTitle("Doughnut")
+        self.show()
+
+    def update_currency_list(self, currencies):
+        for currency in currencies:
+            if self.currencyList.findText(currency) == -1:
+                self.currencyList.addItem(currency)
+
+        self.currencyList.model().sort(0)
+
+    def check_check_state(self, i):
+        if not i.isCheckable():  # Skip data columns.
+            return
+
+        currency = i.text()
+        checked = i.checkState() == Qt.Checked
+
+        if currency in self._data_visible:
+            if not checked:
+                self._data_visible.remove(currency)
+                self.redraw()
+        else:
+            if checked:
+                self._data_visible.append(currency)
+                self.redraw()
+
+    def get_currency_color(self, currency):
+        if currency not in self._data_colors:
+            self._data_colors[currency] = next(BREWER12PAIRED)
+
+        return self._data_colors[currency]
+
+    def add_data_row(self, currency):
+        citem = QStandardItem()
+        citem.setText(currency)
+        citem.setForeground(QBrush(QColor(
+            self.get_currency_color(currency)
+        )))
+        citem.setColumnCount(2)
+        citem.setCheckable(True)
+        if currency in DEFAULT_DISPLAY_CURRENCIES:
+            citem.setCheckState(Qt.Checked)
+
+        vitem = QStandardItem()
+
+        vitem.setTextAlignment(Qt.AlignRight | Qt.AlignVCenter)
+        self.model.setColumnCount(2)
+        self.model.appendRow([citem, vitem])
+        self.model.sort(0)
+        return citem, vitem
+
+    def get_or_create_data_row(self, currency):
+        if currency not in self._data_items:
+            self._data_items[currency] = self.add_data_row(currency)
+        return self._data_items[currency]
+
+    def mouse_move_handler(self, pos):
+        pos = self.ax.getViewBox().mapSceneToView(pos)
+        self.line.setPos(pos.x())
+        self.update_data_viewer(int(pos.x()))
+
+    def update_data_row(self, currency, value):
+        citem, vitem = self.get_or_create_data_row(currency)
+        vitem.setText("%.4f" % value)
+
+    def update_data_viewer(self, d):
+        try:
+            data = self.data[d]
+        except IndexError:  # Skip update if out of bounds.
+            return
+
+        if not data:  # Skip update if we have no data.
+            return
+
+        for k, v in data.items():
+            self.update_data_row(k, v)
+
+    def change_base_currency(self, currency):
+        self.base_currency = currency
+        self.refresh_historic_rates()
+
+    def refresh_historic_rates(self):
+        if self.worker:
+            # If we have a current worker, send a kill signal
+            self.worker.signals.cancel.emit()
+
+        # Prefill our data store with None ('no data')
+        self.data = [None] * HISTORIC_DAYS_N
+
+        self.worker = UpdateWorker(self.base_currency)
+        # Handle callbacks with data and trigger refresh.
+        self.worker.signals.data.connect(self.result_data_callback)
+        self.worker.signals.finished.connect(self.refresh_finished)
+        self.worker.signals.progress.connect(self.progress_callback)
+        self.threadpool.start(self.worker)
+
+    def result_data_callback(self, n, rates):
+        self.data[n] = rates
+
+        # Refresh plot if we haven't for >1 second.
+        if (self._last_updated is None or
+            self._last_updated < datetime.now() - timedelta(seconds=1)
+            ):
+            self.redraw()
+            self._last_updated = datetime.now()
+
+    def progress_callback(self, progress):
+        self.progress.setValue(progress)
+
+    def refresh_finished(self):
+        self.worker = False
+        self.redraw()
+        # Ensure all currencies we know about are in the dropdown list now.
+        self.update_currency_list(self._data_items.keys())
+
+    def redraw(self):
+        """
+        Process data from store and prefer to draw.
+        :return:
+        """
+        today = date.today()
+        plotd = defaultdict(list)
+        x_ticks = []
+
+        tick_step_size = HISTORIC_DAYS_N / 6
+        # Pre-process data into lists of x, y values
+        for n, data in enumerate(self.data):
+            if data:
+                for currency, v in data.items():
+                    plotd[currency].append((-n, v))
+
+            when = today - timedelta(days=n)
+            if (n-tick_step_size//2) % tick_step_size == 0:
+                x_ticks.append((-n, when.strftime('%d-%m')))
+
+        # Update the plot
+        keys = sorted(plotd.keys())
+        y_min, y_max = sys.maxsize, 0
+
+        for currency in keys:
+            x, y = zip(*plotd[currency])
+
+            if currency in self._data_visible:
+                y_min = min(y_min, *y)
+                y_max = max(y_max, *y)
+            else:
+                x, y = [], []
+
+            if currency in self._data_lines:
+                self._data_lines[currency].setData(x, y)
+            else:
+                self._data_lines[currency] = self.ax.plot(
+                    x, y,  # Unpack a list of tuples into two lists, passed as individual args.
+                    pen=pg.mkPen(
+                        self.get_currency_color(currency),
+                        width=2
+                    )
+                )
+
+
+        self.ax.setLimits(yMin=y_min * 0.9, yMax=y_max * 1.1)
+        self.ax.getAxis('bottom').setTicks([x_ticks,[]])
+
+
+if __name__ == '__main__':
+
+    app = QApplication([])
+    window = MainWindow()
+    app.exec_()
\ No newline at end of file
diff --git a/translate/MainWindow.py b/translate/MainWindow.py
index 045fa22..4a4d8ce 100644
--- a/translate/MainWindow.py
+++ b/translate/MainWindow.py
@@ -55,6 +55,6 @@ class Ui_MainWindow(object):
 
     def retranslateUi(self, MainWindow):
         _translate = QtCore.QCoreApplication.translate
-        MainWindow.setWindowTitle(_translate("MainWindow", "Translataaaar"))
+        MainWindow.setWindowTitle(_translate("MainWindow", "Translataarrr"))
         self.translateButton.setToolTip(_translate("MainWindow", "Translate"))
 
diff --git a/translate/mainwindow.ui b/translate/mainwindow.ui
index ad04383..9f72565 100644
--- a/translate/mainwindow.ui
+++ b/translate/mainwindow.ui
@@ -11,7 +11,7 @@
    </rect>
   </property>
   <property name="windowTitle">
-   <string>Translataaaar</string>
+   <string>Translataarrr</string>
   </property>
   <widget class="QWidget" name="centralwidget">
    <layout class="QHBoxLayout" name="horizontalLayout">