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# [BQN](https://mlochbaum.github.io/BQN/), 33 bytes<sup>[SBCS](https://github.com/mlochbaum/BQN/blob/master/commentary/sbcs.bqn)</sup>

```
>(⌽(⊑¨55↑+˜⊸+⊔'0'+⌽⊸⌊⊸⌊)¨˜1↓↑)↕28
```

[Run online!](https://mlochbaum.github.io/BQN/try.html#code=PijijL0o4oqRwqg1NeKGkSvLnOKKuCviipQnMCcr4oy94oq44oyK4oq44oyKKcKoy5wx4oaT4oaRKeKGlTI4)

Minimum of [barycentric coordinates](https://en.wikipedia.org/wiki/Barycentric_coordinate_system) placed according to a skew transformation on two of them. So, the `min(i,j,27-i-j)` thing pretty much. The result is a character matrix.

The three coordinates are height, distance from left, and distance from right, and always sum to 27. In row `i` the height is `27-i`, and the possible values for the other two coordinates range from `0` to `i`. So reversing (`⌽`) `↕28` gives the height and non-empty [Prefixes](https://mlochbaum.github.io/BQN/doc/prefixes.html) (`↑`) are the horizontal coordinates. The location of a number is the height plus *twice* the distance from the left. [Group](https://mlochbaum.github.io/BQN/doc/group.html) (`⊔`) places each character at its location, giving a list of lists of characters—always zero or one of them in this case.

```
>(⌽(⊑¨55↑+˜⊸+⊔'0'+⌽⊸⌊⊸⌊)¨˜1↓↑)↕28
                              ↕28  # Range 0…27
 (⌽                       1↓↑)     # Function train
                            ↑      # Prefixes of ↕28
                          1↓       #   but not the first (empty) one
  ⌽                                # Reversed range 27…0
                         ˜         # Exchange the order
   (                   )¨          # On each pair (e.g. 𝕨=3…27 and 𝕩=25)
                  ⌽⊸⌊⊸⌊            # Min-with-reverse 𝕨; min with 𝕩
              '0'+                 # Digit character from number
         +˜⊸+                      # Locations (2×𝕨)+𝕩
             ⊔                     # Put characters at locations
      55↑                          # Extend to length 55
    ⊑¨                             # First at each location, or space
>                                  # Merge axes to give a matrix
```

It's tacit: see [trains](https://mlochbaum.github.io/BQN/doc/train.html) and [Before](https://mlochbaum.github.io/BQN/tutorial/combinator.html#before-and-after) as usual.