diff --git a/common/build.h b/common/build.h
index 1d28793..9da8ec3 100644
--- a/common/build.h
+++ b/common/build.h
@@ -1,2 +1,2 @@
 /* This file is generated by git */
-#define BUILD "634"
+#define BUILD "635"
diff --git a/webui/modal.js b/webui/modal.js
new file mode 100644
index 0000000..ac87b3c
--- /dev/null
+++ b/webui/modal.js
@@ -0,0 +1,183 @@
+
+
+/**
+ * A class for creating a modal window
+ */
+class Modal {
+    constructor(width, height, title, okText, cancelText, okFunc) {
+        if (Modal._instance)
+            throw 'Only one instance of this class can exist at once';
+        Modal._instance = this;
+        this.main = this.create('div', null, {
+            'position': 'absolute',
+            'top': '0',
+            'bottom': '0',
+            'left': '0',
+            'right': '0',
+        });
+        this.overlay = this.create('div', null, {
+            'position': 'absolute',
+            'top': '0',
+            'bottom': '0',
+            'left': '0',
+            'right': '0',
+            'background-color': 'black',
+            'opacity': '0.5'
+        });
+        this.overlay.click(() => { this.close(); });
+        document.body.append(this.main);
+        this.main.append(this.overlay);
+        let dialogOffset = (this.overlay.offsetHeight - height) / 2;
+        this.dialog = this.create('div', null, {
+            'padding': '0.2em',
+            'outline': '1px solid black',
+            'font-weight': 'bold',
+            'text-align': 'center',
+            'background-color': 'white',
+            'margin': 'auto',
+            'position': 'relative',
+            'margin-top': dialogOffset + 'px',
+            'width': width + 'px',
+            'height': height + 'px',
+            'z-index': '3'
+        });
+        this.main.prepend(this.dialog);
+        if (title) {
+            let heading = this.create('h3', title);
+            this.dialog.append(heading);
+        }
+        let canceler = this.create('div', null, {
+            'position': 'absolute',
+            'bottom': '0.5em',
+            'right': '1em',
+        });
+        this.dialog.append(canceler);
+        if (okText) {
+            let okButton = this.create('button', okText)
+            okButton.click(okFunc);
+            canceler.append(okButton);
+        }
+        if (cancelText) {
+            let cancelButton = this.create('button', cancelText)
+            cancelButton.click(evt => {
+                this.close();
+            });
+            canceler.append(cancelButton);
+        }
+    }
+
+    /**
+     * Creates a new HTML element
+     *
+     * @param element The element type (e.g. div, span, etc)
+     * @param text Text to be inserted into the element. Pass null/undefined
+     *      to leave the element empty
+     * @param style An object containing any additional style attributes to be
+     *      added to the object
+     */
+    create(element, text, style) {
+        let el = document.createElement(element);
+        if (text)
+            el.innerText = text
+        if (style) {
+            for (let key in style)
+                el.style.setProperty(key, style[key]);
+        }
+        return el;
+    }
+    close() {
+        this.main.remove();
+        Modal._instance = null;
+    }
+}
+
+/**
+ * Creates a modal for loading & storing flags
+ */
+class FlagsModal extends Modal {
+    constructor() {
+        super(400, 300, 'Presets', null, 'Cancel');
+        let builtinPresets = {
+            'Standard': 'IVIAAVCAKACAAAAAAAAAAEAA',
+            'Fast Standard': 'IVIAAVCAKACFAAAAAAAAAIAA',
+            'Easy Standard': 'IVIAAVCFKACACQAAAAAAAZAA',
+            'Tiebreaker': 'IVKQAVCEKEAFKRIAAAAAAYAA',
+        }
+        this.dialog.append(this.create('div', 'Save', {
+            'font-weight': 'normal',
+            'margin-bottom': '0.5em',
+        }));
+        let saver = this.create('div');
+        let nameBox = this.create('input');
+        nameBox.placeholder = 'Preset Name';
+        nameBox.setAttribute('maxlength', '50');
+        saver.append(nameBox);
+        let saveButton = this.create('button', 'Save current');
+        saver.append(saveButton)
+        this.dialog.append(saver);
+        this.dialog.append(saver)
+        let flagSelect = this.create('select');
+        for (let [key,value] of Object.entries(builtinPresets)) {
+            let opt = this.create('option', key)
+            opt.value = value
+            flagSelect.append(opt);
+        }
+        this.dialog.append(this.create('div', 'Load/Delete', {
+            'font-weight': 'normal',
+            'margin-top': '2em',
+            'margin-bottom': '0.5em',
+        }));
+        let loader = this.create('div');
+        let storedPresets = localStorage.getItem('storedPresets');
+        if (storedPresets) {
+            storedPresets = JSON.parse(storedPresets);
+            for (let [key,value] of Object.entries(storedPresets)) {
+                let opt = this.create('option', key)
+                opt.value = value
+                flagSelect.append(opt);
+            }
+        } else {
+            storedPresets = {};
+        }
+        loader.append(flagSelect)
+        let loadButton = this.create('button', 'Load preset', {
+            'margin-left': '1em',
+        });
+        let deleteButton = this.create('button', 'Delete Preset', {
+            'margin-left': '1em',
+        });
+        loader.append(this.create('br'));
+        loader.append(this.create('br'));
+        loader.append(loadButton)
+        loader.append(deleteButton)
+        this.dialog.append(loader)
+        // init events
+        saveButton.click(evt => {
+            if (nameBox.value) {
+                storedPresets[nameBox.value] = Interface.getFlags()
+                localStorage.setItem('storedPresets',
+                    JSON.stringify(storedPresets));
+                this.close()
+            }
+        });
+        loadButton.click(evt => {
+            Interface.setFlags(flagSelect.value)
+            this.close();
+        });
+        deleteButton.click(evt => {
+            let option = flagSelect.selectedOptions[0]
+            delete storedPresets[option.innerText];
+            localStorage.setItem('storedPresets',
+                JSON.stringify(storedPresets));
+            option.remove();
+        });
+        deleteButton.disabled = 'true';
+        flagSelect.change(function() {
+            if (this.selectedIndex < Object.keys(builtinPresets).length) {
+                deleteButton.disabled = 'true';
+            } else {
+                deleteButton.disabled = undefined;
+            }
+        });
+    }
+}