alphaPlan · Programming in a Data World · Cheat-sheet 04

Build it

Assemble Turtle, loops, functions, lists and events into one small game that runs and that you can show to someone.

Ideas to remember

01The goal is a working game, not a polished one: a turtle that moves when you press a key, something to reach or avoid, and a way to win or lose.
02Choose one idea and stick with it; a finished small game beats an unfinished ambitious one.
03Build in milestones and run after each one, so you always have something that works.
04Every part you have learned is in the scaffold: a turtle stored in a variable, one small function per action, and event listeners that connect a key to a function.
05Keep the positions of food or walls in a list so you can add and remove them.
06In the presentation, show the game running first, then say what it does in one sentence, what was hardest, and what you would add next.

player.penup(): Lifts the pen so the player square moves without leaving a line.
player.sety(player.ycor() + step): Moves the player up by step pixels; setx and xcor do the same sideways.
step = 20: How far the player moves on each key press; make it bigger to move faster.
place_food(): Drops the food turtle at a random spot with random.randint(-9, 9) * 20.
player.distance(food) < 20: True when the player has reached the food; then the score goes up and the next food appears somewhere new.

Design it on paper first: one or two sentences on what the game is, what the player does, and how you win or lose.
Get one turtle moving with the arrow keys before adding anything else.
Add the goal, then a score and an ending condition, then polish with colours, a title and a start message.
Add check_food() to the end of each of your four move functions so every move checks for food.
Change one thing at a time in the scaffold, such as step or the colours, and understand each change before reusing it.

Do not try to write the whole game at once; without small steps you lose the safety of always having something that works.
It is fine if something is unfinished, but say what you would add next instead of hiding it.
The showing matters, not only the code: leave time to present, not just to build.

Found something unclear, outdated or improvable? Suggest an improvement