diff --git a/html/images/space.svg b/html/images/space.svg
index dfb353a..e8ed1ff 100644
--- a/html/images/space.svg
+++ b/html/images/space.svg
@@ -59,7 +59,7 @@
       </g>
     </g>
 
-    <polygon id="wall" points="-20,-20 -20,-30 30,-30 30,30 -20,30 -20,20 20,20 20,-20" />
+    <polygon id="wall" points="-20,-20 -20,-30 30,-30 30,30 -10,40 -20,30 20,20 20,-20" />
     <!-- <rect id="rect1" x="30" y="30" width="20" height="20"/> -->
     <g id="lines">
     </g>
@@ -156,6 +156,7 @@
     function updateTriangles([positionX, positionY]) {
       const delim = ' ';
       const className = 'clockwise-orientation';
+      const visible = [];
 
       triangles.forEach(t => {
         const attr = t.getAttribute('points').split(delim);
@@ -174,11 +175,14 @@
         }
 
         t.classList[cwOrientation ? "add" : "remove"](className);
+        if (cwOrientation) visible.push(t);
         // i think i can also discard obtuse triangles?
 
         // if all the triangles are obtuse, i only need to check the nearest corner for a collision
         // otherwise, i need to check only the acute triangles
       });
+
+      return visible;
     }
 
     const lines = lineContainer.querySelectorAll('line');
@@ -286,6 +290,10 @@
       animate(timestamp);
     }
 
+    function distance(x1, y1, x2, y2) {
+      return Math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2);
+    }
+
     function animate(timestamp) {
       const delta = timestamp - zero;
       const elapsed = timestamp - previous;
@@ -294,11 +302,11 @@
       if (delta >= 1000) {
         fps.innerText = frameCount;
 
-        info.innerText = `velocity ${velocity}\n`
-          + 'bullets\nx\ty\tvx\tvy\n'
-          + bullets.map(b => {
-            return `${b.x.toFixed(2)}\t${b.y.toFixed(2)}\t${b.vx.toFixed(2)}\t${b.vy.toFixed(2)}`;
-          }).join("\n");
+        // info.innerText = `velocity ${velocity}\n`
+        //   + 'bullets\nx\ty\tvx\tvy\n'
+        //   + bullets.map(b => {
+        //     return `${b.x.toFixed(2)}\t${b.y.toFixed(2)}\t${b.vx.toFixed(2)}\t${b.vy.toFixed(2)}`;
+        //   }).join("\n");
 
         zero = timestamp;
         frameCount = 0;
@@ -306,6 +314,7 @@
         frameCount++;
       }
 
+
       let degrees = getRotate(gun);
 
       if (rotate > 0) gun.style.transform = `rotate(${(+degrees + rotationSpeed * elapsed) % 360}deg)`;
@@ -338,7 +347,26 @@
 
       updateBullets(elapsed);
       // updateLines(position);
-      updateTriangles(position);
+      const visibleTriangles = updateTriangles(position);
+
+      // info.innerText = [...visibleTriangles].map(t => {
+      //   const [[ax, ay], [bx, by], [shipx, shipy]] =
+      //     t.getAttribute('points').split(' ').map(n => n.split(',').map(n => +n));
+      //
+      //   const da = distance(ax, ay, shipx, shipy);
+      //   const db = distance(bx, by, shipx, shipy);
+      //   const dc = distance(ax, ay, bx, by);
+      //   const s = (1 / 2) * (da + db + dc);
+      //   const hc = (2 / dc) * Math.sqrt(s * (s - da) * (s - db) * (s - dc));
+      //
+      //   const alpha = Math.acos((db**2 + dc**2 - da**2) / (2 * db * dc));
+      //   const beta = Math.acos((da**2 + dc**2 - db**2) / (2 * da * dc));
+      //
+      //   const PI = Math.PI / 2;
+      //   const acute = alpha < PI && beta < PI;
+      //
+      //   return `${da.toFixed(2)} ${db.toFixed(2)} ${dc.toFixed(2)} ${hc.toFixed(2)} ${alpha.toFixed(2)} ${beta.toFixed(2)}`;
+      // }).join('\n');
 
       // can do this after side collision detection
       // const ts = updateTriangles(position);
@@ -359,7 +387,25 @@
         return shipBody.isPointInFill(cornerPt);
       });
 
-      wall.setAttribute('fill', cornerCollision ? 'red' : 'black');
+      const PI = Math.PI / 2;
+      const shipRadius = 5;
+      const sideCollision = [...visibleTriangles].reduce((acc, t) => {
+        const [[ax, ay], [bx, by], [shipx, shipy]] =
+          t.getAttribute('points').split(' ').map(n => n.split(',').map(n => +n));
+
+        const da = distance(ax, ay, shipx, shipy);
+        const db = distance(bx, by, shipx, shipy);
+        const dc = distance(ax, ay, bx, by);
+        const s = (1 / 2) * (da + db + dc);
+        const hc = (2 / dc) * Math.sqrt(s * (s - da) * (s - db) * (s - dc));
+        const alpha = Math.acos((db**2 + dc**2 - da**2) / (2 * db * dc));
+        const beta = Math.acos((da**2 + dc**2 - db**2) / (2 * da * dc));
+        const acute = alpha < PI && beta < PI;
+
+        return acute ? [...acc, hc] : acc;
+      }, []).some(h => h <= shipRadius);
+
+      wall.setAttribute('fill', cornerCollision || sideCollision ? 'red' : 'black');
       hitbox.style.transform = `translate(${positionX}px, ${positionY}px)`;
 
       // if (+y < 200)