diff --git a/src/html/component/functions-editor/editor-tile/editor-tile.ts b/src/html/component/functions-editor/editor-tile/editor-tile.ts
index cd97f29..102ba49 100644
--- a/src/html/component/functions-editor/editor-tile/editor-tile.ts
+++ b/src/html/component/functions-editor/editor-tile/editor-tile.ts
@@ -1,4 +1,4 @@
-import { css, LitElement, type PropertyValues, unsafeCSS } from 'lit'
+import { css, LitElement, unsafeCSS } from 'lit'
 import { property, query, state } from 'lit/decorators.js'
 import style_less from './editor-tile.less?inline'
 import { Essentiality, type IFunctionData, type IRegulationData, Monotonicity } from '../../../util/data-interfaces'
@@ -52,10 +52,6 @@ export abstract class EditorTile extends LitElement {
     this.aceEditor.renderer.attachToShadowRoot()
   }
 
-  protected updated (_changedProperties: PropertyValues): void {
-    super.updated(_changedProperties)
-  }
-
   protected updateEditor (name: string, func: string): void {
     if (this.nameField !== undefined) {
       this.nameField.value = name
diff --git a/src/html/component/functions-editor/editor-tile/function-tile.ts b/src/html/component/functions-editor/editor-tile/function-tile.ts
index e0f524a..ce6cfe5 100644
--- a/src/html/component/functions-editor/editor-tile/function-tile.ts
+++ b/src/html/component/functions-editor/editor-tile/function-tile.ts
@@ -9,6 +9,7 @@ import ace, { type Ace } from 'ace-builds'
 import langTools from 'ace-builds/src-noconflict/ext-language_tools'
 import 'ace-builds/esm-resolver'
 import { EditorTile } from './editor-tile'
+import { functionDebounceTimer } from '../../../util/config'
 
 library.add(faTrash, faMagnifyingGlass)
 
@@ -38,6 +39,7 @@ export class FunctionTile extends EditorTile {
         })))
       }
     })
+    this.aceEditor.setOption('placeholder', '$f_' + this.functions[this.index].id + '(...)')
   }
 
   protected firstUpdated (_changedProperties: PropertyValues): void {
@@ -54,8 +56,7 @@ export class FunctionTile extends EditorTile {
       bubbles: true,
       composed: true
     }))
-  },
-  300
+  }, functionDebounceTimer
   )
 
   functionUpdated = debounce(() => {
@@ -67,8 +68,7 @@ export class FunctionTile extends EditorTile {
       bubbles: true,
       composed: true
     }))
-  },
-  300
+  }, functionDebounceTimer
   )
 
   async removeVariable (): Promise<void> {
diff --git a/src/html/component/functions-editor/editor-tile/variable-tile.ts b/src/html/component/functions-editor/editor-tile/variable-tile.ts
index 9e2a649..bf012fa 100644
--- a/src/html/component/functions-editor/editor-tile/variable-tile.ts
+++ b/src/html/component/functions-editor/editor-tile/variable-tile.ts
@@ -9,6 +9,7 @@ import ace, { type Ace } from 'ace-builds'
 import langTools from 'ace-builds/src-noconflict/ext-language_tools'
 import 'ace-builds/esm-resolver'
 import { EditorTile } from './editor-tile'
+import { functionDebounceTimer } from '../../../util/config'
 library.add(faTrash, faMagnifyingGlass)
 
 @customElement('variable-tile')
@@ -40,6 +41,7 @@ export class VariableTile extends EditorTile {
       'constant.language': this.variables.map(v => v.id).join('|'),
       'support.function.dom': this.functions.map(f => f.id).join('|')
     })
+    this.aceEditor.setOption('placeholder', '$f_' + this.variables[this.index].id + '(...)')
   }
 
   private getVariables (): IVariableData[] {
@@ -55,8 +57,7 @@ export class VariableTile extends EditorTile {
       bubbles: true,
       composed: true
     }))
-  },
-  300
+  }, functionDebounceTimer
   )
 
   functionUpdated = debounce(() => {
@@ -68,8 +69,7 @@ export class VariableTile extends EditorTile {
       bubbles: true,
       composed: true
     }))
-  },
-  300
+  }, functionDebounceTimer
   )
 
   toggleEssentiality (regulation: IRegulationData): void {
diff --git a/src/html/component/root-component/root-component.ts b/src/html/component/root-component/root-component.ts
index 789dd6d..1a131a2 100644
--- a/src/html/component/root-component/root-component.ts
+++ b/src/html/component/root-component/root-component.ts
@@ -112,19 +112,18 @@ export default class RootComponent extends LitElement {
     this.data = this.data.copy({ functions })
   }
 
-  private saveData (variables: IVariableData[], regulations: IRegulationData[], layout: ILayoutData): void {
-    // save variable/regulation/layout data, leave functions as is
-
-    // sort nodes to keep alphabetical order in lists
+  private saveVariables (variables: IVariableData[]): void {
     variables.sort((a, b) => (a.id > b.id ? 1 : -1))
+    this.data = this.data.copy({ variables })
+  }
+
+  private saveRegulations (regulations: IRegulationData[]): void {
     regulations.sort((a, b) => (a.source + a.target > b.source + b.target ? 1 : -1))
+    this.data = this.data.copy({ regulations })
+  }
 
-    this.data = ContentData.create({
-      variables,
-      regulations,
-      layout,
-      functions: this.data.functions
-    })
+  private saveLayout (layout: ILayoutData): void {
+    this.data = this.data.copy({ layout })
   }
 
   renameVariable (event: Event): void {
@@ -140,7 +139,7 @@ export default class RootComponent extends LitElement {
       id: data.id,
       name: data.name
     }
-    this.saveData(variables, this.data.regulations, this.data.layout)
+    this.saveVariables(variables)
   }
 
   private addVariable (event: Event): void {
@@ -160,7 +159,7 @@ export default class RootComponent extends LitElement {
       name: data.name,
       function: ''
     })
-    this.saveData(variables, this.data.regulations, this.data.layout)
+    this.saveVariables(variables)
   }
 
   private addRegulation (event: Event): void {
@@ -177,7 +176,7 @@ export default class RootComponent extends LitElement {
       essential: data.essential,
       monotonicity: data.sign
     })
-    this.saveData(this.data.variables, regulations, this.data.layout)
+    this.saveRegulations(regulations)
   }
 
   private async removeVariable (event: Event): Promise<void> {
@@ -187,16 +186,14 @@ export default class RootComponent extends LitElement {
   }
 
   #onVariableRemoved (data: VariableData): void {
-    this.saveData(
-      this.data.variables.filter((variable) => variable.id !== data.id),
-      this.data.regulations,
-      this.data.layout
+    this.saveVariables(
+      this.data.variables.filter((variable) => variable.id !== data.id)
     )
   }
 
   private adjustRegEditor (): void {
     const visible = this.visibleTabs()
-    if (window.outerWidth <= 800 || visible.includes(this.tabs[0])) return
+    if (window.outerWidth <= 800 || !visible.includes(this.tabs[0])) return
     window.dispatchEvent(new CustomEvent('adjust-graph', {
       detail: {
         tabCount: visible.length
@@ -224,11 +221,12 @@ export default class RootComponent extends LitElement {
 
   #onNodePositionChanged (data: LayoutNodeData): void {
     // TODO: add support for layouts
-    this.data.layout.set(data.variable, {
+    const layout = new Map(this.data.layout)
+    layout.set(data.variable, {
       x: data.px,
       y: data.py
     })
-    this.saveData(this.data.variables, this.data.regulations, this.data.layout)
+    this.saveLayout(layout)
   }
 
   private setVariableId (event: Event): void {
@@ -256,7 +254,7 @@ export default class RootComponent extends LitElement {
         regulations[index].target = data.new_id
       }
     })
-    this.saveData(variables, this.data.regulations, this.data.layout)
+    this.saveVariables(variables)
 
     // TODO: this refresh is a temporary solution to get potentially modified update function expressions
     aeonState.model.refreshVariables()
@@ -275,7 +273,7 @@ export default class RootComponent extends LitElement {
       ...regulations[index],
       essential: data.essential
     }
-    this.saveData(this.data.variables, regulations, this.data.layout)
+    this.saveRegulations(regulations)
   }
 
   private toggleRegulationMonotonicity (event: Event): void {
@@ -291,7 +289,7 @@ export default class RootComponent extends LitElement {
       ...regulations[index],
       monotonicity: data.sign
     }
-    this.saveData(this.data.variables, regulations, this.data.layout)
+    this.saveRegulations(regulations)
   }
 
   private setVariableFunction (event: Event): void {
@@ -307,7 +305,7 @@ export default class RootComponent extends LitElement {
       ...variables[variableIndex],
       function: data.update_fn
     }
-    this.saveData(variables, this.data.regulations, this.data.layout)
+    this.saveVariables(variables)
   }
 
   private async removeRegulation (event: Event): Promise<void> {
@@ -317,18 +315,14 @@ export default class RootComponent extends LitElement {
   }
 
   #onRegulationRemoved (data: RegulationData): void {
-    this.saveData(
-      this.data.variables,
-      this.data.regulations.filter((regulation) => regulation.source !== data.regulator || regulation.target !== data.target),
-      this.data.layout
+    this.saveRegulations(
+      this.data.regulations.filter((regulation) => regulation.source !== data.regulator || regulation.target !== data.target)
     )
   }
 
   #onVariablesRefreshed (variables: VariableData[]): void {
-    this.saveData(
-      variables.map(v => { return { ...v, function: v.update_fn } }),
-      this.data.regulations,
-      this.data.layout
+    this.saveVariables(
+      variables.map(v => { return { ...v, function: v.update_fn } })
     )
   }
 
@@ -337,7 +331,7 @@ export default class RootComponent extends LitElement {
     layoutNodes.forEach(layoutNode => {
       layout.set(layoutNode.variable, { x: layoutNode.px, y: layoutNode.py })
     })
-    this.saveData(this.data.variables, this.data.regulations, layout)
+    this.saveLayout(layout)
   }
 
   #onRegulationsRefreshed (regulations: RegulationData[]): void {
@@ -350,7 +344,7 @@ export default class RootComponent extends LitElement {
         monotonicity: data.sign
       }
     })
-    this.saveData(this.data.variables, regs, this.data.layout)
+    this.saveRegulations(regs)
   }
 
   async loadDummy (): Promise<void> {
diff --git a/src/html/component/undo-redo/undo-redo.less b/src/html/component/undo-redo/undo-redo.less
index 024302d..d34232c 100644
--- a/src/html/component/undo-redo/undo-redo.less
+++ b/src/html/component/undo-redo/undo-redo.less
@@ -18,12 +18,19 @@
   .uk-button {
     background: rgb(34, 34, 34);
   }
-
-
 }
 
 @media (prefers-color-scheme: light) {
   .uk-button {
     background: rgb(222, 222, 222);
   }
+
+  .uk-button:hover {
+    background: rgb(200, 200, 200);
+  }
+
+
+  .fa-arrow-left, .fa-arrow-right {
+    color: black;
+  }
 }
diff --git a/src/html/component/undo-redo/undo-redo.ts b/src/html/component/undo-redo/undo-redo.ts
index 9ba68ca..3754d46 100644
--- a/src/html/component/undo-redo/undo-redo.ts
+++ b/src/html/component/undo-redo/undo-redo.ts
@@ -29,9 +29,9 @@ export default class UndoRedo extends LitElement {
   render (): TemplateResult {
     return html`
       <div class="undo-redo uk-flex-nowrap">
-        <button class="uk-button uk-button-secondary uk-button-small"
+        <button class="uk-button uk-button-secondary uk-button-small ${!this.canUndo ? 'disabled' : ''}"
                 @click=${aeonState.undoStack.undo} ?disabled=${!this.canUndo}>${icon(faArrowLeft).node}</button>
-        <button class="uk-button uk-button-secondary uk-button-small"
+        <button class="uk-button uk-button-secondary uk-button-small ${!this.canRedo ? 'disabled' : ''}"
                 @click=${aeonState.undoStack.redo} ?disabled=${!this.canRedo}>${icon(faArrowRight).node}</button>
       </div>
     `
diff --git a/src/html/util/config.ts b/src/html/util/config.ts
index 583102e..4e9b5ed 100644
--- a/src/html/util/config.ts
+++ b/src/html/util/config.ts
@@ -36,3 +36,5 @@ export const tabList: TabData[] = [
     icon: 'a'
   })
 ]
+
+export const functionDebounceTimer = 1000