diff --git a/languages/befunge93/renderer.tsx b/languages/befunge93/renderer.tsx
index 14d9ebe..02c2f07 100644
--- a/languages/befunge93/renderer.tsx
+++ b/languages/befunge93/renderer.tsx
@@ -1,10 +1,18 @@
-import { Card, Colors, Icon, IconName } from "@blueprintjs/core";
+import * as React from "react";
+import { Colors, Icon, IconName } from "@blueprintjs/core";
 import { RendererProps } from "../types";
+import { Box } from "../ui-utils";
 import { Bfg93Direction, Bfg93RS } from "./constants";
 
 /** Common border color for dark and light, using transparency */
 export const BorderColor = Colors.GRAY3 + "55";
 
+// Parameters for cell sizing, balanced to span the full row width
+// Constraint: `(width% + 2 * margin%) * ROWSIZE = 100%`
+const ROWSIZE = 8;
+const CELL_WIDTH = "12%";
+const CELL_MARGIN = "5px 0.25%";
+
 const styles = {
   placeholderDiv: {
     height: "100%",
@@ -33,9 +41,9 @@ const styles = {
   },
   stackItem: {
     // Sizing
-    width: "10%",
-    height: "40px",
-    margin: "5px 0.25%",
+    width: CELL_WIDTH,
+    margin: CELL_MARGIN,
+    height: "50px",
     // Center-align values
     display: "flex",
     justifyContent: "center",
@@ -50,10 +58,10 @@ const DirectionIcons: { [k: string]: IconName } = {
   [Bfg93Direction.DOWN]: "arrow-down",
 };
 
-const StackItem = ({ value }: { value: number }) => {
-  const cellStyle = { ...styles.stackItem };
-  return <Card style={cellStyle}>{value}</Card>;
-};
+/** Component for displaying a single stack item */
+const StackItem = React.memo(({ value }: { value: number }) => {
+  return <Box style={styles.stackItem}>{value}</Box>;
+});
 
 export const Renderer = ({ state }: RendererProps<Bfg93RS>) => {
   if (state == null)
@@ -64,7 +72,6 @@ export const Renderer = ({ state }: RendererProps<Bfg93RS>) => {
       <div style={styles.dirnContainer}>
         <span style={{ fontWeight: "bold", marginRight: 5 }}>Direction: </span>
         <Icon icon={DirectionIcons[state.direction]} />
-        {/* <span style={{ marginLeft: 10 }} /> */}
         <span style={{ marginLeft: 30, fontWeight: "bold", marginRight: 5 }}>
           String mode:{" "}
         </span>
diff --git a/languages/brainfuck/common.ts b/languages/brainfuck/common.ts
index 9aaef30..cbdd1cd 100644
--- a/languages/brainfuck/common.ts
+++ b/languages/brainfuck/common.ts
@@ -81,9 +81,12 @@ export const editorTokensProvider: MonacoTokensProvider = {
 };
 
 /** Serialize tape from object format into linear array */
-export const serializeTapeMap = (tape: BFRS["tape"]): number[] => {
+export const serializeTapeMap = (
+  tape: BFRS["tape"],
+  minCells: number = 0
+): number[] => {
   const cellIdxs = Object.keys(tape).map((s) => parseInt(s, 10));
-  const maxCellIdx = Math.max(15, ...cellIdxs);
+  const maxCellIdx = Math.max(minCells - 1, ...cellIdxs);
   const linearTape: number[] = Array(maxCellIdx + 1).fill(0);
   cellIdxs.forEach((i) => (linearTape[i] = tape[i] || 0));
   return linearTape;
diff --git a/languages/brainfuck/renderer.tsx b/languages/brainfuck/renderer.tsx
index 73e5aa0..ac4d82c 100644
--- a/languages/brainfuck/renderer.tsx
+++ b/languages/brainfuck/renderer.tsx
@@ -1,14 +1,17 @@
-import { Card, Colors } from "@blueprintjs/core";
-import { CSSProperties } from "react";
-import { useDarkMode } from "../../ui/providers/dark-mode-provider";
+import * as React from "react";
 import { RendererProps } from "../types";
+import { Box } from "../ui-utils";
 import { BFRS, serializeTapeMap } from "./common";
 
-// Colors used as background of active cells
-const darkActiveBG = Colors.DARK_GRAY2;
-const lightActiveBG = Colors.LIGHT_GRAY3;
+/** Number of cells shown in a single row */
+const ROWSIZE = 8;
 
-const styles: { [k: string]: CSSProperties } = {
+// Parameters for cell sizing, balanced to span the full row width
+// Constraint: `(width% + 2 * margin%) * ROWSIZE = 100%`
+const CELL_WIDTH = "12%";
+const CELL_MARGIN = "5px 0.25%";
+
+const styles: { [k: string]: React.CSSProperties } = {
   container: {
     padding: 10,
     height: "100%",
@@ -19,9 +22,9 @@ const styles: { [k: string]: CSSProperties } = {
   },
   cell: {
     // Sizing
-    width: "12%",
+    width: CELL_WIDTH,
+    margin: CELL_MARGIN,
     height: "50px",
-    margin: "5px 0.25%",
     // Center-align values
     display: "flex",
     justifyContent: "center",
@@ -30,22 +33,24 @@ const styles: { [k: string]: CSSProperties } = {
 };
 
 /** Component for displaying a single tape cell */
-const Cell = ({ value, active }: { value: number; active: boolean }) => {
-  const { isDark } = useDarkMode();
-  const cellStyle = { ...styles.cell };
-  const activeBg = isDark ? darkActiveBG : lightActiveBG;
-  if (active) {
-    cellStyle.backgroundColor = activeBg;
-    cellStyle.fontWeight = "bold";
+const Cell = React.memo(
+  ({ value, active }: { value: number; active: boolean }) => {
+    return (
+      <Box
+        intent={active ? "active" : "plain"}
+        style={{ ...styles.cell, fontWeight: active ? "bold" : undefined }}
+      >
+        {value}
+      </Box>
+    );
   }
-  return <Card style={cellStyle}>{value}</Card>;
-};
+);
 
 /** Renderer for Brainfuck */
 export const Renderer = ({ state }: RendererProps<BFRS>) => {
   return (
     <div style={styles.container}>
-      {serializeTapeMap(state?.tape || {}).map((num, i) => (
+      {serializeTapeMap(state?.tape || {}, 2 * ROWSIZE).map((num, i) => (
         <Cell value={num} key={i} active={(state?.pointer || 0) === i} />
       ))}
     </div>
diff --git a/languages/shakespeare/renderer/character-row.tsx b/languages/shakespeare/renderer/character-row.tsx
index 741e34a..a30cd46 100644
--- a/languages/shakespeare/renderer/character-row.tsx
+++ b/languages/shakespeare/renderer/character-row.tsx
@@ -1,5 +1,5 @@
+import { Box } from "../../ui-utils";
 import { CharacterValue } from "../common";
-import { SimpleTag } from "./utils";
 
 type Props = {
   name: string;
@@ -13,9 +13,9 @@ export const CharacterRow = (props: Props) => {
     <div style={{ margin: "20px 10px" }}>
       <div>
         <b style={{ marginRight: 5 }}>{name}:</b>{" "}
-        <pre style={{ display: "inline" }}>{value.value}</pre>
+        <pre style={{ display: "inline", marginRight: 15 }}>{value.value}</pre>
         {value.stack.map((v, i) => (
-          <SimpleTag key={i}>{v}</SimpleTag>
+          <Box key={i}>{v}</Box>
         ))}
       </div>
       <div></div>
diff --git a/languages/shakespeare/renderer/topbar.tsx b/languages/shakespeare/renderer/topbar.tsx
index 07c7533..cbf0640 100644
--- a/languages/shakespeare/renderer/topbar.tsx
+++ b/languages/shakespeare/renderer/topbar.tsx
@@ -1,5 +1,6 @@
-import { Tag, Text } from "@blueprintjs/core";
-import { SimpleTag } from "./utils";
+import React from "react";
+import { Text } from "@blueprintjs/core";
+import { Box } from "../../ui-utils";
 
 const styles = {
   charChip: {
@@ -22,20 +23,16 @@ export const TopBar = (props: Props) => {
 
   const characterChips =
     charactersOnStage.length === 0 ? (
-      <Tag large minimal>
-        The stage is empty
-      </Tag>
+      <Box>The stage is empty</Box>
     ) : (
-      charactersOnStage.map((character) => {
-        return (
-          <SimpleTag
-            key={character}
-            intent={character === currSpeaker ? "active" : undefined}
-          >
-            {character}
-          </SimpleTag>
-        );
-      })
+      charactersOnStage.map((character) => (
+        <Box
+          key={character}
+          intent={character === currSpeaker ? "active" : "plain"}
+        >
+          {character}
+        </Box>
+      ))
     );
 
   return (
@@ -46,9 +43,9 @@ export const TopBar = (props: Props) => {
           <Text tagName="span" style={styles.questionText}>
             Answer to question:
           </Text>
-          <SimpleTag intent={questionState ? "success" : "danger"}>
+          <Box intent={questionState ? "success" : "danger"}>
             {questionState ? "yes" : "no"}
-          </SimpleTag>
+          </Box>
         </>
       )}
     </div>
diff --git a/languages/shakespeare/renderer/utils.tsx b/languages/ui-utils.tsx
similarity index 56%
rename from languages/shakespeare/renderer/utils.tsx
rename to languages/ui-utils.tsx
index a1f901d..ddba4c8 100644
--- a/languages/shakespeare/renderer/utils.tsx
+++ b/languages/ui-utils.tsx
@@ -1,41 +1,43 @@
+import { CSSProperties } from "react";
 import { Colors } from "@blueprintjs/core";
-import { useDarkMode } from "../../../ui/providers/dark-mode-provider";
+import { useDarkMode } from "../ui/providers/dark-mode-provider";
 
 const backgroundColorsLight = {
-  success: Colors.GREEN3,
-  danger: Colors.RED3,
-  plain: Colors.GRAY3,
-  active: Colors.DARK_GRAY1,
+  success: Colors.GREEN5,
+  danger: Colors.RED5,
+  plain: Colors.LIGHT_GRAY1,
+  active: Colors.GRAY4,
 };
 
 const backgroundColorsDark = {
-  success: Colors.GREEN3,
-  danger: Colors.RED3,
-  plain: Colors.GRAY3,
-  active: Colors.LIGHT_GRAY5,
+  success: Colors.GREEN1,
+  danger: Colors.RED1,
+  plain: Colors.DARK_GRAY5,
+  active: Colors.GRAY1,
 };
 
 const foregroundColorsLight = {
-  success: Colors.GREEN2,
-  danger: Colors.RED2,
+  success: Colors.GREEN1,
+  danger: Colors.RED1,
   plain: Colors.DARK_GRAY1,
-  active: Colors.LIGHT_GRAY5,
+  active: Colors.DARK_GRAY1,
 };
 
 const foregroundColorsDark = {
   success: Colors.GREEN5,
   danger: Colors.RED5,
   plain: Colors.LIGHT_GRAY5,
-  active: Colors.DARK_GRAY1,
+  active: Colors.LIGHT_GRAY5,
 };
 
 /**
- * Utility component that renders a tag similar to BlueprintJS tags, but underneath
- * is just a single span tag with no frills and high performance.
+ * Utility component for rendering a simple general-purpose stylable box. Useful
+ * for performance-critical components in visualisation renderers.
  */
-export const SimpleTag = (props: {
+export const Box = (props: {
   children: React.ReactNode;
-  intent?: "success" | "danger" | "active";
+  intent?: "plain" | "success" | "danger" | "active";
+  style?: CSSProperties;
 }) => {
   const { isDark } = useDarkMode();
   const intent = props.intent == null ? "plain" : props.intent;
@@ -49,9 +51,9 @@ export const SimpleTag = (props: {
         margin: 5,
         padding: "5px 10px",
         borderRadius: 3,
-        backgroundColor:
-          backgroundMap[intent] + (intent === "active" ? "aa" : "55"),
+        backgroundColor: backgroundMap[intent],
         color: foregroundMap[intent],
+        ...props.style,
       }}
     >
       {props.children}