diff --git a/builtins.ts b/builtins.ts
index 332811e..d60d906 100644
--- a/builtins.ts
+++ b/builtins.ts
@@ -104,7 +104,7 @@ const faux = {
 	pset: setPixelColor,
 	map: (mapSheet: number, tileX: number, tileY: number, screenX: number, screenY: number, tileW: number, tileH: number) => {
 		const originalSpritesheet = getSpritesheet() ?? 0;
-		getMapSheet(mapSheet).forEach(([sprSheet, spr], i) => {
+		getMapSheet(mapSheet).values.forEach(([sprSheet, spr], i) => {
 			const x = i%64;
 			const y = Math.floor(i/64);
 			if (x >= tileX && y >= tileY && x < tileX + tileW && y < tileY + tileH) {
@@ -119,19 +119,19 @@ const faux = {
 		if (x < 0 || x >= 64 || y < 0 || y >= 64) {
 			return undefined;
 		}
-		return getMapSheet(mapSheet)[y*64+x][0];
+		return getMapSheet(mapSheet).get(x, y)[0];
 	},
 	mgetspr: (mapSheet: number, x: number, y: number) => {
 		if (x < 0 || x >= 64 || y < 0 || y >= 64) {
 			return undefined;
 		}
-		return getMapSheet(mapSheet)[y*64+x][1];
+		return getMapSheet(mapSheet).get(x, y)[1];
 	},
 	mset: (mapSheet: number, x: number, y: number, sprSheet: number, spr: number) => {
 		if (x < 0 || x >= 64 || y < 0 || y >= 64) {
 			return;
 		}
-		getMapSheet(mapSheet)[y*64+x] = [sprSheet, spr];
+		getMapSheet(mapSheet).set(x, y, [sprSheet, spr]);
 	},
 	// Input
 	[CHAR.UP]: K.ARROW_UP,
diff --git a/maptab.ts b/maptab.ts
index 6c90b90..43ec71a 100644
--- a/maptab.ts
+++ b/maptab.ts
@@ -30,18 +30,22 @@ const state = {
 		setSheet(page.activeSheet, "map", val);
 	},
 	setInPatch(i: number, sprsheet: number, sprite: number) {
-		const xx = this.selectedPatch%overviewW;
-		const yy = Math.floor(this.selectedPatch/overviewW);
-		const cell = (yy*patchH+Math.floor(i/patchW))*overviewW*patchW+xx*patchW+i%patchW;
-		this.map[cell] = [sprsheet, sprite];
+		const xx = patchW*(this.selectedPatch%overviewW);
+		const yy = patchH*Math.floor(this.selectedPatch/overviewW);
+		const cellVal = this.map.subgrid(xx, yy, patchW, patchH).values[i];
+		cellVal[0] = sprsheet
+		cellVal[1] = sprite;
+		// const cell = (yy*patchH+Math.floor(i/patchW))*overviewW*patchW+xx*patchW+i%patchW;
+		// this.map[cell] = [sprsheet, sprite];
 	},
 	get patch() {
-		const xx = this.selectedPatch%overviewW;
-		const yy = Math.floor(this.selectedPatch/overviewW);
-		return Array(overviewH).fill(0).flatMap((_, i) => {
-			const start = (yy*patchH+i)*overviewW*patchW+xx*patchW;
-			return this.map.slice(start, start+patchW);
-		})
+		const xx = patchW*(this.selectedPatch%overviewW);
+		const yy = patchH*Math.floor(this.selectedPatch/overviewW);
+		return this.map.subgrid(xx, yy, patchW, patchH);
+		// return Array(overviewH).fill(0).flatMap((_, i) => {
+		// 	const start = (yy*patchH+i)*overviewW*patchW+xx*patchW;
+		// 	return this.map.slice(start, start+patchW);
+		// })
 	}
 }
 
@@ -139,7 +143,7 @@ const draw = () => {
 
 	// Draw the current patch
 	fillRect(patchX-1, patchY-1, (patchW*spriteW)+2, (patchH*spriteH)+2, COLOR.BLACK);
-	state.patch.forEach(([sprsheet, sprite], i) => {
+	state.patch.values.forEach(([sprsheet, sprite], i) => {
 		const spriteX = patchX+spriteW*(i%patchW);
 		const spriteY = patchY+spriteH*Math.floor(i/patchW);
 		if (getSheet(sprsheet).sheet_type === "spritesheet") {
diff --git a/sheet.ts b/sheet.ts
index bc0096d..0fa93ef 100644
--- a/sheet.ts
+++ b/sheet.ts
@@ -1,4 +1,5 @@
 import { getCart } from "./cart.ts";
+import { LinearGrid } from "./util.ts";
 // import { runCode, addToContext } from "./runcode.ts";
 
 // "code" | "spritesheet" | "map" | "sfx" | "patterns" | "fonts"
@@ -50,5 +51,5 @@ export const getMapSheet = (sheet: number) => {
 	if (sheet_type !== "map") {
 		throw "Trying to use a non-map sheet as a map."
 	}
-	return value;
+	return LinearGrid(value, 64);
 }
\ No newline at end of file
diff --git a/util.ts b/util.ts
index b305c95..929117b 100644
--- a/util.ts
+++ b/util.ts
@@ -44,4 +44,38 @@ export const drawTransparentRect = (x: number, y: number, w: number, h: number)
 		const jy = Math.floor(j/w);
 		setPixelColor(x+jx, y+jy, (jx+jy)%2 ? COLOR.BLACK : COLOR.DARKGRAY);
 	})
-}
\ No newline at end of file
+}
+
+export const subgrid = <T>(array: Array<T>, gridW: number, x: number, y: number, w: number, h: number): Array<T> => {
+	return Array(h).fill(0).flatMap((_, i) => {
+		const start = (y+i)*gridW+x;
+		return array.slice(start, start+w);
+	})
+}
+
+export const LinearGrid = <T>(array: Array<T>, gridW: number) => {
+	return {
+		get(x: number, y: number) {
+			return array[this.coordsToIndex(x, y)]
+		},
+		getIndex(i: number) {
+			return array[i];
+		},
+		set(x: number, y: number, value: T) {
+			array[this.coordsToIndex(x, y)] = value;
+		},
+		setIndex(i: number, value: T) {
+			array[i] = value;
+		},
+		values: array,
+		indexToCoords: (i: number) => {
+			return [i%gridW, Math.floor(i/gridW)];
+		},
+		coordsToIndex: (x: number, y: number) => {
+			return y*gridW+x;
+		},
+		// TODO: make alterations to subgrid affect parent grid
+		subgrid: (x: number, y: number, w: number, h: number) => LinearGrid(subgrid(array, gridW, x, y, w, h), w),
+	}
+}
+