layer][z] = (z < (bufSize - rowSize * n)) ? this.p[layer][z + (rowSize * n)] : 0;
				}
			}
			return;
		}
		if (op == 0x00FB) {
			// scroll right 4 pixels
			var rowSize = this.hires ? 128 : 64;
			for(var layer = 0; layer < 2; layer++) {
				if ((this.plane & (layer+1)) == 0) { continue; }
				for(var a = 0; a < this.p[layer].length; a += rowSize) {
					for(var b = rowSize-1; b >= 0; b--) {
						this.p[layer][a + b] = (b > 3) ? this.p[layer][a + b - 4] : 0;
					}
				}
			}
			return;
		}
		if (op ==