diff --git a/src/main.rs b/src/main.rs
index 26d6cf3..f2ba7e2 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -60,6 +60,7 @@ fn main() {
 	rl.set_window_min_size(640, 480);
 	rl.set_mouse_cursor(MouseCursor::MOUSE_CURSOR_CROSSHAIR);
 	rl.set_exit_key(None);
+	rl.set_trace_log(TraceLogLevel::LOG_WARNING);
 
 	let mut textures = Textures::default();
 	textures.load_dir("assets", &mut rl, &thread);
diff --git a/src/marble_engine.rs b/src/marble_engine.rs
index e49afe0..55395d0 100644
--- a/src/marble_engine.rs
+++ b/src/marble_engine.rs
@@ -102,7 +102,7 @@ impl Machine {
 		// reset wires
 		for y in 0..self.board.height() {
 			for x in 0..self.board.width() {
-				if let Tile::Powerable(_, state) = self.board.get_mut_unchecked((x, y).into()) {
+				if let Some(Tile::Powerable(_, state)) = self.board.get_mut((x, y).into()) {
 					*state = false;
 				}
 			}
@@ -113,95 +113,96 @@ impl Machine {
 			let marble_pos = self.marbles[i];
 			let tile = self.board.get_or_blank(marble_pos);
 
-			if let Tile::Marble { value, dir } = tile {
-				let next_pos = dir.step(marble_pos);
-				if !self.board.in_bounds(next_pos) {
-					continue;
+			let Tile::Marble { value, dir } = tile else {
+				continue;
+			};
+			let next_pos = dir.step(marble_pos);
+			if !self.board.in_bounds(next_pos) {
+				continue;
+			}
+			let mut new_tile = None;
+			let Some(target) = self.board.get_mut(next_pos) else {
+				continue;
+			};
+			match target {
+				Tile::Blank => {
+					*target = tile;
+					self.marbles[i] = next_pos;
+					new_tile = Some(Tile::Blank);
 				}
-				let mut new_tile = None;
-				let target = self.board.get_mut_unchecked(next_pos);
-				match target {
-					Tile::Blank => {
+				Tile::Digit(d) => {
+					let new_val = value.wrapping_mul(10).wrapping_add(*d as MarbleValue);
+					*target = Tile::Marble {
+						value: new_val,
+						dir,
+					};
+					self.marbles[i] = next_pos;
+					new_tile = Some(Tile::Blank);
+				}
+				Tile::Powerable(PTile::Bag, _) => {
+					to_remove.push(i);
+					new_tile = Some(Tile::Blank);
+				}
+				Tile::Marble {
+					value: _other_value,
+					dir: other_dir,
+				} => {
+					// bounce off other marbles
+					if *other_dir != dir {
+						new_tile = Some(Tile::Marble {
+							value,
+							dir: dir.opposite(),
+						});
+						*other_dir = dir;
+					}
+				}
+				Tile::Powerable(PTile::Trigger, state) => {
+					// triggers activate even if the marble can't move past it
+					// making it stay on permanently (or until the marble is knocked away)
+					*state = true;
+					triggers.push(next_pos);
+					let far_pos = dir.step(next_pos);
+					if let Some(target) = self.board.get_blank_mut(far_pos) {
 						*target = tile;
-						self.marbles[i] = next_pos;
+						self.marbles[i] = far_pos;
 						new_tile = Some(Tile::Blank);
 					}
-					Tile::Digit(d) => {
-						let new_val = value.wrapping_mul(10).wrapping_add(*d as MarbleValue);
+				}
+				Tile::Arrow(arrow_dir) => {
+					let far_pos = arrow_dir.step(next_pos);
+					let arrow_dir = *arrow_dir;
+					if let Some(target) = self.board.get_blank_mut(far_pos) {
+						self.marbles[i] = far_pos;
 						*target = Tile::Marble {
-							value: new_val,
-							dir,
+							value,
+							dir: arrow_dir,
 						};
-						self.marbles[i] = next_pos;
 						new_tile = Some(Tile::Blank);
+					} else if far_pos == marble_pos {
+						// always bounce on reverse arrow
+						new_tile = Some(Tile::Marble {
+							value,
+							dir: dir.opposite(),
+						});
 					}
-					Tile::Powerable(PTile::Bag, _) => {
-						to_remove.push(i);
-						new_tile = Some(Tile::Blank);
-					}
-					Tile::Marble {
-						value: _other_value,
-						dir: other_dir,
-					} => {
-						// bounce off other marbles
-						if *other_dir != dir {
-							new_tile = Some(Tile::Marble {
-								value,
-								dir: dir.opposite(),
-							});
-							*other_dir = dir;
-						}
-					}
-					Tile::Powerable(PTile::Trigger, state) => {
-						*state = true;
-						triggers.push(next_pos);
-						let far_pos = dir.step(next_pos);
-						if let Some(Tile::Blank) = self.board.get(far_pos) {
-							self.board.set(far_pos, Tile::Marble { value, dir });
-							self.marbles[i] = far_pos;
-							new_tile = Some(Tile::Blank);
-						}
-					}
-					Tile::Arrow(arrow_dir) => {
-						let far_pos = arrow_dir.step(next_pos);
-						let arrow_dir = *arrow_dir;
-						if let Some(Tile::Blank) = self.board.get(far_pos) {
-							self.marbles[i] = far_pos;
-							self.board.set(
-								far_pos,
-								Tile::Marble {
-									value,
-									dir: arrow_dir,
-								},
-							);
-							new_tile = Some(Tile::Blank);
-						} else if far_pos == marble_pos {
-							// bounce on reverse arrow
-							new_tile = Some(Tile::Marble {
-								value,
-								dir: dir.opposite(),
-							});
-						}
-					}
-					Tile::Mirror(mirror) => {
-						let new_dir = mirror.new_dir(dir);
-						let far_pos = new_dir.step(next_pos);
-						let far_target = self.board.get_mut_unchecked(far_pos);
-						if let Tile::Blank = far_target {
-							*far_target = Tile::Marble {
-								value,
-								dir: new_dir,
-							};
-							self.marbles[i] = far_pos;
-							new_tile = Some(Tile::Blank);
-						}
-					}
-					_ => (),
 				}
+				Tile::Mirror(mirror) => {
+					let new_dir = mirror.new_dir(dir);
+					let far_pos = new_dir.step(next_pos);
+					if let Some(far_target) = self.board.get_blank_mut(far_pos) {
+						*far_target = Tile::Marble {
+							value,
+							dir: new_dir,
+						};
+						self.marbles[i] = far_pos;
+						new_tile = Some(Tile::Blank);
+					}
+				}
+				_ => (),
+			}
 
-				if let Some(t) = new_tile {
-					*self.board.get_mut_unchecked(marble_pos) = t;
-				}
+			if let Some(t) = new_tile {
+				*self.board.get_mut(marble_pos).unwrap() = t;
 			}
 		}
 		let mut offset = 0;
@@ -217,10 +218,9 @@ impl Machine {
 	}
 
 	fn propagate_power(&mut self, dir: Direction, pos: Pos) {
-		if !self.board.in_bounds(pos) {
+		let Some(tile) = self.board.get_mut(pos) else {
 			return;
-		}
-		let tile = self.board.get_mut_unchecked(pos);
+		};
 		let front_pos = dir.step(pos);
 		if let Tile::Powerable(tile, state) = tile {
 			if let PTile::Trigger = tile {
@@ -244,19 +244,19 @@ impl Machine {
 					}
 				}
 				PTile::Bag => {
-					if let Some(Tile::Blank) = self.board.get(front_pos) {
-						*self.board.get_mut_unchecked(front_pos) = Tile::Marble { value: 0, dir };
+					if let Some(front) = self.board.get_blank_mut(front_pos) {
+						*front = Tile::Marble { value: 0, dir };
 						self.marbles.push(front_pos);
 					}
 				}
 				PTile::Input => {
-					if self.input_index < self.input.len()
-						&& self.board.get_or_blank(front_pos).is_blank()
-					{
-						let value = self.input[self.input_index] as MarbleValue;
-						*self.board.get_mut_unchecked(front_pos) = Tile::Marble { value, dir };
-						self.marbles.push(front_pos);
-						self.input_index += 1;
+					if let Some(front) = self.board.get_blank_mut(front_pos) {
+						if self.input_index < self.input.len() {
+							let value = self.input[self.input_index] as MarbleValue;
+							self.input_index += 1;
+							*front = Tile::Marble { value, dir };
+							self.marbles.push(front_pos);
+						}
 					}
 				}
 				PTile::Math(op) => {
@@ -265,9 +265,8 @@ impl Machine {
 					let pos_b = dir.right().step(pos);
 					let val_a = self.board.get_or_blank(pos_a).read_value();
 					let val_b = self.board.get_or_blank(pos_b).read_value();
-					if (!self.board.get_or_blank(pos_a).is_blank()
-						|| !self.board.get_or_blank(pos_b).is_blank())
-						&& self.board.get_or_blank(front_pos).is_blank()
+					if !self.board.get_or_blank(pos_a).is_blank()
+						|| !self.board.get_or_blank(pos_b).is_blank()
 					{
 						let value = match op {
 							MathOp::Add => val_a.wrapping_add(val_b),
@@ -277,13 +276,17 @@ impl Machine {
 							MathOp::Rem => val_a.checked_rem(val_b).unwrap_or_default(),
 						};
 						// println!("{op:?} a:{val_a} b:{val_b}");
-						*self.board.get_mut_unchecked(front_pos) = Tile::Marble { value, dir };
-						self.marbles.push(front_pos);
+						if let Some(front) = self.board.get_blank_mut(front_pos) {
+							*front = Tile::Marble { value, dir };
+							self.marbles.push(front_pos);
+						}
 					}
 				}
 				PTile::Flipper => {
-					let m = self.board.get_mut_unchecked(front_pos);
-					match m {
+					let Some(target) = self.board.get_mut(front_pos) else {
+						return;
+					};
+					match target {
 						Tile::Powerable(PTile::Wire(wire_type), _) => {
 							*wire_type = match *wire_type {
 								WireType::Vertical => WireType::Horizontal,
diff --git a/src/marble_engine/board.rs b/src/marble_engine/board.rs
index 26064d8..82d9247 100644
--- a/src/marble_engine/board.rs
+++ b/src/marble_engine/board.rs
@@ -108,15 +108,14 @@ impl Board {
 		}
 	}
 
-	pub fn get_mut_unchecked(&mut self, p: Pos) -> &mut Tile {
+	pub fn get_blank_mut(&mut self, p: Pos) -> Option<&mut Tile> {
 		if self.in_bounds(p) {
-			&mut self.rows[p.y as usize][p.x as usize]
-		} else {
-			panic!(
-				"position {p:?} out of bounds, size is {}x{}",
-				self.width, self.height
-			);
+			let tile = &mut self.rows[p.y as usize][p.x as usize];
+			if tile == &Tile::Blank {
+				return Some(tile);
+			}
 		}
+		None
 	}
 
 	pub fn set(&mut self, p: Pos, tile: Tile) {