That sounds like a classic epsilon problem – the physics step is letting a small numerical slip through. Here’s a quick, teachable approach you can share with others, too. First, make sure your collision detection uses a small but explicit tolerance. Instead of testing “a < b”, test “a < b + ε” where ε is something like 1e‑6 or a few times the smallest unit of your world. Next, in the collision response, clamp the position of the box to the floor plane rather than just nudging it back. If the box’s y‑coordinate is below the floor by more than your tolerance, set it exactly to the floor height. That eliminates the tiny “portal” you’re seeing. For floating‑point quirks, remind people that double precision gives you about 15 decimal places of accuracy. If your world coordinates are in the millions, you’re already losing granularity. A good trick is to use a fixed‑point approach or a “relative” coordinate system: keep all positions relative to a moving origin or use integer units. And always separate the physics tick from rendering; if you’re interpolating between steps, avoid mixing the two. In a lesson, walk through a simple example: start with a single box falling, show the raw positions, then step through the correction code. That visual cue helps students see where the epsilon sneaks in. And remember: a little math, a little clamping, and a generous tolerance, and you’ll keep that floor solid and the portal closed.

Sure thing, here’s a little more fleshed‑out version you can drop into your tick loop. It keeps the logic separate from rendering and shows where the clamp happens: ```cpp const float EPS = 1e-6f; // small tolerance const float FLOOR_Y = 0.0f; // y‑coordinate of the floor void physicsStep(Body& b, float dt) { // Simple gravity b.vel.y -= 9.81f * dt; // Integrate position b.pos += b.vel * dt; // Collision with floor if (b.pos.y < FLOOR_Y + EPS) { b.pos.y = FLOOR_Y; // clamp to exact floor height b.vel.y = 0.0f; // reset vertical velocity } } ``` In your main loop, call `physicsStep` first, then draw: ```cpp while (running) { float dt = getDeltaTime(); physicsStep(body, dt); // update physics render(); // separate from physics } ``` That should keep the portal shut. If you still see a slip, play with `EPS` or switch to a fixed‑point scheme for the positions. Let me know how it goes!