Previously on...
In the last article I learned a ton about Pulp and all the wonderful ways it makes developing simple games for the Playdate real easy.
Even for simple games, though, it's tough to make a fun game without a little programming.
That's where PulpScript comes in.
Thus far, I've studied a few games' script files.
Many were easy to interpret.
But there were commands I didn't fully understand.
I hope that reading the official PulpScript Docs fills in all those gaps...and sheds plenty more light on what I can do with this handy API.
Table of Contents
- Woah! This document is nearly three times as long as the Pulp Docs!
- Looks like there is a section on the aspects of the language, then several sections all about the many functions made available by the API
General
This language has:
- Variables
- Event Handlers
- Persistant Storage
- Math
- Control Flow
- Comments
- Strings
- Loops
- Dates and Times
I've dabbled in all of that!
Interesting excerpts
All game logic must occur inside an event handler.
All variables are globally scoped.
All uninitialized variables have a default value of
0
.Variables can hold a number or a string. Strings must be wrapped in double quotes.
Compound expressions are not supported.
Oh, that explains why I kept seeing overly nested if...then
clauses in all the games: because there's not logical AND or OR in PulpScript!
String comparisons are case-sensitive.
Callbacks and event handlers can be exited early with the done statement
Variables can be persisted across launches using the
store
andrestore
functions.
Oh, so that's what those keywords were doing!
-
call
triggers an event for the current tile -
emit
triggers an event for all tiles that implement that particular event - No
for
loops, but there is awhile
loop
Functions
The built-in functions I recall:
load
finish
loop
update
confirm
cancel
crank
draw
interact
collect
When these functions are called:
- on the game, or once on the game
- on each room, or the current room
- on each tile or the current tile
- on the Player each time they move or collide with a tile
- on an item when the player collides with that tile
The menu-related functions:
change
select
dismiss
invalid
I wonder how the cursor is controlled in a Pulp game...especially such that a series of menu items in-game can be selected using any of the buttons on the Playdate.
The functions I now know exist:
-
start
,enter
,exit
bump
-
dock
,undock
any
mimic
The event
object
Throughout the built-in functions, the event
object may have one or more of the following read-only members
a.k.a. properties:
-
dx
- horizontal direction: -1 (up), 0 (same), 1 (down) -
dy
- vertical direction: -1 (up), 0 (same), 1 (down) -
tx
- X coordinate of the target tile relative to the room -
ty
- Y coordinate of the target tile relative to the room -
x
- X coordinate of the tile -
y
- Y coordinate of the tile -
tile
- name of the current tile -
room
- name of the current room -
px
- current player X coordinate -
py
- current player Y coordinate -
aa
- absolute angle of the crank -
ra
- relative angle of the crank (degree difference relative to the previous frame) -
frame
- number of frames elapsed since game start -
ax
- accelerometer's X value -
ay
- accelerometer's Y value -
az
- accelerometer's Z value -
orientation
- a string describing the Playdate's current orientation -
option
- currently selected option's name -
game
- name of the game -
player
- name of the player tile
The config
object
This object can be used to override the default settings through its writable members.
Things that can be changed include:
- Input delays
- Camera settings
- Color of out-of-bounds tiles
- Time delays
- Text interaction and display timings
The datetime
object
Lots of great variables for use in tracking time!
String formatting
Hooray for use of curly braces to interpolate values inside a string!
And very cool that strings can be padded on each side a specific amount.
And putting tiles in a string? Hmm. I'm not sure how I would use that, but cool.
Functions again!
-
log
works as expected -
dump
is a great troubleshooting tactic -
say
presents a message...and can be positioned and re-sized! -
ask
is like aswitch
statement where each clause is anoption
and the body of a reaction - I wonder how
menu
differs in appearance and use thanask
-
fin
is the true game-ending prompt, eh? At least because it emits theon finish do
event -
swap
replaces a tile's artwork with that of another -
frame
andframeIndex
capture a frame from a tile's animation set -
play
starts - optionally interrupting? - a tile's series of animation frames -
wait
creates a delay, with exception to therun
loop...? And there's a caveat about preventing player movement? I don't quite understand those parts yet. -
shake
is a nice touch! -
tell
lets me manipulate one tile from another -
call
andemit
do the same thing, but one for a single tile and the other for any/all applicable tiles -
mimic
seems interesting, but not sure what a use case is at this moment -
ignore
andlisten
are great player-input-disabling functions! -
act
is very interesting: perform some foreshadowing! -
draw
can only be called from the Player'sdraw
event...interesting. -
hide
makes it impossible to draw the player. So...like, to simulate a tunnel? -
window
draws a window frame. Cool? -
label
places text on the room and not in a window or prompt: so for UI elements, perhaps? -
fill
draws rectangles! -
crop
essentially creates a mask over the room within which drawing can occur -
goto
moves the player to a position in a room -
sound
plays a sound -
once
plays a song and stops, optionally doing more things when the song has finished -
loop
plays a song again and again -
stop
ends the currently playing song -
btm
adjusts the beat of the song -
store
sets a value in storage when a game or room is entered or exited -
restore
sets a value from one in storage -
toss
deletes values from storage -
random
generates a random integer -
floor
rounds a decimal down to the nearest integer -
ceil
rounds a decimal up to the nearest integer -
round
rounds a decimal to the closest integer -
sine
,cosine
,tangent
do geometry things based on a number -
radians
converts a number from degrees to radians -
degrees
converts a number from radians to degrees -
invert
draws the opposite color and returns the current mode -
solid
identifies a tile as solid or not -
type
identifies a tile's type -
id
identifies a tile from its position or name -
name
identifies a tile from its position or id
Lots of feelings
- So many event functions!
- So many event object members!
- So many other functions!
- Tons of knowledge gaps filled!
- Lots of questions about some of these functions and event handlers!
- Excitement to
log
tons of things in tons of event handlers to learn first-hand how all this works!
What next?
- Try to find a comprehensive tutorial on building a game in Pulp?
- Start with the list of links on the Pulp help page?
- Or see what's on Youtube?
- Or skip all that and just play around in the editor myself, struggling gleefully the whole time?
It all sounds like it's gonna be a ton of fun...especially now that I'm more familiar with PulpScript and how Tiles work.
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