Named block sequences¶

A sequence can be an ordinary Python list. Give it a name that describes its purpose, then pass it directly to a script or control block.

from itchy import control, events, looks, sensing
from itchy.control import if_
from itchy import move

from itchy.game import Command

reset_player: list[Command] = [
    move.to(0, 0),
    score.reset(),
]

collect_coin: list[Command] = [
    score.add(1),
    looks.hide(),
]

events.on_start(reset_player)
if_(sensing.touching(player)).then_(collect_coin)

The snippets assume the variables and sprite references from the enclosing game. There is no sequence-specific wrapper or syntax.

Name both branches¶

from itchy import control
from itchy.control import if_
decide_turn = (
    if_(health > 0)
    .then_(move_right)
    .else_(reset_player)
)

Both branch bodies can be named Python lists. The underscore in if_ and else_ avoids Python keywords; .then_(...) makes the conditional command complete.

Compose lists¶

from itchy import events
from itchy.game import Steps

prepare_round: list[Steps] = [
    reset_player,
    prepare_coin,
]

events.on_start(prepare_round, play_round)

Command is the union of individual command descriptions. Steps accepts a command or a nested Python sequence of steps. Use list[Command] for flat command lists and list[Steps] for lists containing other lists. The builders flatten nested sequences while preserving order.

Each use produces fresh Scratch block IDs. Reusing a list does not make the exported scripts share a block node. Builders capture their sequences when called: changing a list later does not change an already constructed script.

Parameterized generators¶

Use a function when a sequence needs arguments:

from itchy import control, events
from itchy.control import if_
from itchy import move

from itchy.game import action

@action
def walk(distance: float, count: int):
    return control.repeat(count, move.x(distance))

events.on_start(walk(4, 3), walk(-2, 2))

The decorator preserves argument types and normalizes the generated result into a command tuple. ty rejects walk("far", 3). @action runs during generation and expands blocks inline; it does not create a Scratch custom-block definition.