Jev Blocks

Craft: a Jev Blocks challenge

Jev places every piece of a falling-blocks puzzle with one call. The craft is to set up a game that shows a real decision loop under a real limit, then to find the point where the limit wins.

The decision loop

For each new piece the viewer builds one state text:

• the style line,
• the well as 20 ASCII rows (# filled, . empty),
• column heights, holes, bumpiness and the deepest well,
• the current piece and the next three,
• level, lines, gravity, and what a decision and a move cost,
• a table of every legal placement. The id is r<rotation>c<leftmost column>, for example r1c4.

Then it asks three questions in the same call:

Questions cannot see each other. Shared facts live in the state text.

The honest limit

Time. The piece falls at gravity x (1 + speedup x (level - 1)) rows per second. A decision costs decisionMs. Each rotate or shift costs moveMs. The piece falls the whole time. When it lands, it locks, even if it has not reached the chosen column. The pane marks that as TOO SLOW and counts it under MISSED.

A rough rule: a placement needs decisionMs + (moves + 1) x moveMs. The fall gives free rows / gravity seconds. With 110 ms and 35 ms, a wall placement (about 6 moves) needs about 355 ms. On an empty well that fits up to about 46 rows per second. On a stack 8 rows high it only fits up to about 28. So height and gravity work together, and garbage makes speed bite sooner.

Knobs and what they do

{
  "gravity": 2,        // 0.2 to 40. The starting speed.
  "speedup": 0.5,      // 0 to 2. 0 keeps gravity fixed, which is best for a clean comparison.
  "decisionMs": 110,   // 30 to 1000. Raise it to play a slower model.
  "moveMs": 35,        // 5 to 500.
  "garbageRows": 0,    // 0 to 12.
  "weights": { "I": 1, "O": 1, "T": 1, "S": 1, "Z": 1, "J": 1, "L": 1 },
  "board": [],         // up to 20 rows of 10 characters, '.' or '#', top row first
  "style": "Keep the stack low and flat. Go for four when it is safe."
}

Ideas that make a good challenge:

• Speed test. speedup: 0, then try gravity 10, 25, 40. Add garbageRows: 8 so 40 really bites.
• Slow thinker. Keep gravity at 12 and set decisionMs to 300, then 700. Watch the misses start.
• Dig-out. garbageRows: 10, low gravity, a style line that says dig first.
• Cruel mix. "weights": { "S": 1, "Z": 1 }, or drop the I piece and see what go_for_four says.
• Set piece. Draw a board that is one I piece from four lines and see if Jev takes it.

How to find the breaking point

1. Fix the seed and set speedup to 0.
2. Change one knob, save, let the game run for a minute or so.
3. Read .harness/verdict.json. Look at the summary line and the timing finding (N of the last 50 pieces landed short of their target at G rows/s) and the topout finding.
4. Move the knob and repeat. Report the last setting that played clean and the first that did not.

Checking

node "$JEV_DSH/toolchain/check.mjs"

It prints ok or one error line per problem: a number out of range, weights that are all zero, a board row that is not 10 characters of . and #.

Honesty

• The game is synthetic. The score means nothing outside this pane.
• Without an API key the pane says MOCK. The offline reader is a fixed heuristic. It shows that the plumbing works. It does not show how well live Jev plays. Say which one you measured.
• Never edit .harness/verdict.json, and never tell the person to open a browser or start a server.