((this.plane & (layer+1)) == 0) { continue; }
				for(var z = this.p[layer].length - 1; z >= 0; z--) {
					this.p[layer][z] = (z >= rowSize * n) ? this.p[layer][z - (rowSize * n)] : 0;
				}
			}
			return;
		}
		if ((op & 0xFFF0) == 0x00D0) {
			// scroll up n pixels
			var rowSize = this.hires ? 128 : 64;
			var bufSize = this.hires ? (128 * 64) : (64 * 32);
			for(var layer = 0; layer < 2; layer++) {
				if ((this.plane & (layer+1)) == 0) { continue; }
				for(var z = 0; z < bufSize; z++) {
					this.p[