Game Mechanics and Win/Lose Conditions

Summary

Builds complete game mechanics with collision detection, scoring, lives, and win/lose states. This chapter covers 20 concepts from the learning graph, building on prerequisite concepts from earlier chapters.

Concepts Covered

This chapter covers the following 20 concepts from the learning graph:

1. List Item Access
2. Testing Strategies
3. Debugging Strategies
4. Storytelling Flow
5. Synchronous Broadcast
6. Broadcast Storm
7. Loop Termination
8. Boolean Combination
9. Win Condition
10. Lose Condition
11. Delete From List
12. List Contains
13. High Score List
14. Storyboarding
15. Clone Performance
16. Inventory System
17. Pair Programming
18. Scene Planning
19. Imagine Phase
20. Flowchart

Prerequisites

This chapter builds on concepts from:

• 4. Events, Sequences, and First Scripts
• 7. Variables, Lists, and Data Management
• 8. Animation, Parallelism, and Debugging
• 9. Advanced Control and Operators

---

List Item Access — Getting Specific Items! 📋

List Item Block (Variables → Dark Red)

item (1) of [inventory v]

Reporter: gets the value at a specific position in the list.

List Position Numbers

Lists are 1-indexed — first item is position 1, not 0!

Position	Item
1	First item
2	Second item
3	Third item
...	...
(length of list)	Last item

List Item Examples

Access Specific Item

say (item (1) of [inventory v]) for 2 secs  // Says first item

Loop Through All Items

repeat (length of [inventory v])
    say (item (loop-counter) of [inventory v]) for 1 secs
end

Get Last Item

set [last-item v] to (item (length of [list v]) of [list v])

---

List Item Safety

Always check bounds before accessing!

if < (index) > (length of [list v]) > then
    say [Invalid index!] for 2 secs
else
    say (item (index) of [list v]) for 2 secs
end

---

List Item in Game Mechanics

Use Item from Inventory

when I receive [use-item v]
if < (length of [inventory v]) > 0 > then
    set [item-to-use v] to (item (1) of [inventory v])
    delete (1) of [inventory v]
    // Use the item...
end

Equip Best Weapon

set [best-damage v] to (0)
repeat (length of [weapons v])
    if < (item (loop-counter) of [weapons v]) > (best-damage) > then
        set [best-damage v] to (item (loop-counter) of [weapons v])
        set [best-weapon-index v] to (loop-counter)
    end
end

---

Delete From List — Removing Items! 🗑️

Delete Block (Variables → Dark Red)

delete (1) of [inventory v]

Removes item at specified position — remaining items shift down!

Delete Examples

Remove Used Item

when I receive [use-potion v]
delete (1) of [inventory v]  // Remove first item

Remove Specific Item

delete (3) of [inventory v]  // Remove 3rd item

Clear Entire List

delete all of [inventory v]

Remove by Value (Search + Delete)

repeat (length of [inventory v])
    if < (item (loop-counter) of [inventory v]) = [rotten-apple] > then
        delete (loop-counter) of [inventory v]
    end
end

---

Delete + High Score List

when I receive [new-score v]
if < (score) > (item (1) of [high-scores v]) > then
    insert (score) at (1) of [high-scores v]
    if < (length of [high-scores v]) > 5 > then
        delete (6) of [high-scores v]  // Keep top 5
    end
end

---

List Contains — Is It In There? 🔍

List Contains Block (Variables → Dark Red)

[apple v] in [inventory v]?

Boolean: TRUE if item exists in list, FALSE otherwise.

Contains Examples

Check for Item

if < [key v] in [inventory v]? > then
    say [Door unlocked!] for 2 secs
    broadcast [door-open v]
else
    say [You need a key!] for 2 secs
end

Check for Duplicate Before Adding

if <not < [sword v] in [inventory v]? >> then
    add [sword] to [inventory v]
    say [Got a sword!] for 2 secs
else
    say [Already have a sword!] for 2 secs
end

Check for Quest Item

if < [ancient-scroll v] in [inventory v]? > then
    broadcast [quest-complete v]
end

---

Contains vs Item Access

Block	Returns	Use For
item (1) of [list]	Value at position	Get the actual item
[item] in [list]?	True/False	Check existence

---

High Score List — Top Players! 🏆

High Score List Structure

high-scores list:
[0] 10500  (1st place)
[1] 9800   (2nd place)
[2] 8750   (3rd place)
[2] 7200   (4th place)
[3] 5500   (5th place)

High Score Logic

when green flag clicked
delete all of [high-scores v]
repeat 5
    add (0) to [high-scores v]
end
show list [high-scores v]

when I receive [game-over v]
if < (score) > (item (1) of [high-scores v]) > then
    // New high score!
    insert (score) at (1) of [high-scores v]
    delete (6) of [high-scores v]  // Keep top 5
    say [NEW HIGH SCORE!] for 3 secs
end

---

High Score Display

Display Method	Code
List on stage	show list [high-scores]
Custom display	repeat 5: say (join [#] (join (loop-counter) (join [: ] (item (loop-counter) of [high-scores])))) for 2 secs
With names	Store join [name] (join [: ] (score)) in list

---

High Score Features

Feature	Implementation
Top 5/10	delete (6) of [list] to trim
Names + Scores	Store join [name] (join [: ] (score))
Date achieved	Add timestamp to entry
Level-specific	Separate list per level

---

Testing Strategies — Quality Assurance! 🧪

What Are Testing Strategies?

Testing strategies = systematic ways to find bugs and verify your game works!

Testing Levels

Level	What It Tests	When
Unit test	Single script/block	While coding
Integration test	Multiple scripts together	After adding feature
Playtest	Full game experience	Before sharing
Regression test	Old features still work	After changes
Edge case test	Extreme/unusual inputs	Before release

---

Testing Strategies

Strategy	How To Do It
Boundary testing	Test edges: 0, 1, max, min, -1
Invalid input	Wrong keys, empty lists, divide by 0
Stress test	Spawn 100 clones, run 10 minutes
Permutation test	Try all key combinations
Save/load test	Save, reload, continue game
Multiplayer test	Two keyboards, two players

---

Testing Checklist

Category	Tests
Movement	All directions, edges, collisions, jumping
Controls	All keys, key combos, rapid presses
Physics	Gravity, jumping, falling, slopes
Combat	Damage, knockback, invincibility, death
Scoring	Points, high scores, combos, multipliers
Lives	Lose, gain, game over, invincibility
Levels	Transitions, spawns, completion, secrets
UI	Menus, pause, menus, displays
Audio	Music, SFX, volume, mute
Performance	100 clones, 10 min play, save/load

---

Automated Testing (Custom Blocks)

define test-movement
// Test: Player moves right
go to x: 0 y: 0
repeat 10
    change x by 5
end
if < (x position) = 50 > then
    say [TEST PASS: Movement] for 2 secs
else
    say [TEST FAIL: Movement] for 2 secs
end

define test-collision
// Test: Wall collision
go to x: 220 y: 0
if <touching color [#FF0000]? > then
    say [TEST PASS: Collision] for 2 secs
else
    say [TEST FAIL: Collision] for 2 secs
end

---

Debugging Strategies — Fix Bugs Like a Pro! 🐛

Debugging Workflow

1. REPRODUCE → Make bug happen every time
2. ISOLATE → Which script? Which block?
3. HYPOTHESIZE → "I think the 'change x by' is wrong"
4. TEST → Change ONE thing, test again
5. FIX → Apply correction
6. VERIFY → Test thoroughly, check for new bugs

---

Debugging Tools in Scratch

Tool	How to Use
Block Highlighting	Watch which block glows during execution
Variable Watchers	show variable — see values live on stage
say Debugging	say (variable) for 0.1 secs — live values
wait for Timing	wait 1 secs to slow down and observe
Single Step	Some Scratch versions: step through blocks
Clean Up	Right-click → "Clean up" — aligns blocks

---

Debugging with say (Live Values!)

forever
    say (join [x: ] (x position)) for 0.1 secs
    say (join [y: ] (y position)) for 0.1 secs
    say (join [vel-x: ] (velocity-x)) for 0.1 secs
    say (join [onGround: ] (touching [ground v]?)) for 0.1 secs
    wait 0.1 secs
end

Live dashboard of all important values! 📊

---

Common Bug Patterns & Fixes

Bug Symptom	Likely Cause	Debug Steps
Sprite frozen	forever without wait	Add wait 0.01 secs
Moves wrong way	Wrong sign (+/-)	Check change x by sign
Jumps infinitely	No ground check	Add touching ground?
Stuck in wall	No collision check	Add touching color?
Score not updating	Wrong variable name	Check score vs Score
Clone explosion	No spawn limit	Add cooldown/limit
Lag/freeze	Too many loops	Combine loops, add wait

---

Debugging Strategies

Strategy	How To Apply
Divide and conquer	Disable half the code, test, narrow down
Rubber duck debugging	Explain code to a rubber duck (or friend)
Binary search	Disable half scripts, test, narrow to one script
Minimal reproduction	Create new project with just the buggy part
Print everything	say all variables at each step
Check assumptions	"Is this variable actually 0?" — verify with say

---

Storytelling Flow — Games That Tell Stories! 📖

What Is Storytelling Flow?

Storytelling flow = how your game guides the player through a narrative experience!

Story Structure in Games

Act	Purpose	Game Elements
Setup (Act 1)	Introduce world, character, goal	Tutorial, first level, intro cutscene
Confrontation (Act 2)	Challenges, rising action	Harder levels, new mechanics, mid-boss
Climax (Act 3)	Final challenge, resolution	Final boss, final level, ending cutscene

---

Storytelling Through Gameplay

Story Element	Game Mechanic
Character	Player sprite, customization
Setting	Backdrops, level design
Conflict	Enemies, obstacles, puzzles
Progression	Levels, upgrades, new abilities
Resolution	Win screen, credits, epilogue

---

Storytelling Through Code

when green flag clicked
broadcast [chapter1 v] and wait    // Setup
broadcast [chapter2 v] and wait    // Rising action
broadcast [chapter3 v] and wait    // Climax
broadcast [ending v]               // Resolution

when I receive [chapter1 v]
switch backdrop to [village v]
speak [Our village was peaceful...] and wait
speak [Until the Shadow King came...] and wait
broadcast [chapter1-done v]

when I receive [chapter2 v]
switch backdrop to [forest v]
speak [You must find the three crystals...] and wait
// Gameplay: collect 3 crystals

---

Synchronous Broadcast — Wait for Everyone! 🤝

Broadcast And Wait Recap

broadcast [message v] and wait

Pauses sender until ALL when I receive scripts FINISH.

---

When to Use Synchronous Broadcast

Scenario	Why Sync
Level start	All sprites initialized before gameplay
Cutscene steps	Each line finishes before next
Save game	All data saved before continuing
Multi-phase boss	Phase 1 done before phase 2 starts
Cutscene dialogue	Each character finishes speaking

---

Synchronous Broadcast Example

when green flag clicked
broadcast [initialize v] and wait
wait 1 secs
broadcast [spawn-player v] and wait
broadcast [spawn-enemies v] and wait
broadcast [spawn-ui v] and wait
broadcast [game-ready v]

when I receive [initialize v]
set [score v] to (0)
set [lives v] to (3)

when I receive [spawn-player v]
go to x: -200 y: -100
show

when I receive [spawn-enemies v]
repeat 5
    create clone of [enemy v]
    wait 0.2 secs
end

---

Broadcast Storm — Too Many Messages! ⚡

What Is a Broadcast Storm?

Broadcast storm = too many broadcasts sent too quickly = lag, crashes, unpredictable behavior!

Causes of Broadcast Storms

Cause	Example
Broadcast in forever loop	forever { broadcast [update] }
Recursive broadcasts	A → B, B → A, A → B...
Too many clones broadcasting	100 clones each broadcast
Broadcast in when I receive	Chain reaction

---

Preventing Broadcast Storms

Prevention	How
Rate limit	wait 0.1 secs between broadcasts
Flags	if <not <broadcasting>> then broadcast
Cooldown	set [cooldown v] to (10), change by -1 each frame
Single broadcaster	One "manager" sprite handles all broadcasts

---

Broadcast Storm Example (BAD!)

forever
    broadcast [update v]    // STORM! Thousands per second
end

Broadcast Storm Fix (GOOD!)

forever
    broadcast [update v]
    wait 0.1 secs   // Rate limited!
end

---

Loop Termination — Exiting Loops Properly! 🛑

How Loops End

Loop Type	Terminates When...
repeat (N)	After N iterations
forever	stop [this script] or stop [all]
repeat until <cond>	Condition becomes TRUE
repeat while (custom)	Condition becomes FALSE

---

Loop Termination Blocks

Block	Stops
stop [this script v]	Current script only
stop [all v]	EVERYTHING in project
stop [other scripts in sprite v]	Other scripts in same sprite

---

Loop Termination Examples

Break Out of Forever

forever
    if <key [escape] pressed?> then
        stop [this script v]
    end
    // Game loop code
end

Exit Nested Loop

repeat (10)
    repeat (10)
        if <touching [target v]?> then
            stop [this script v]  // Exits BOTH loops!
        end
    end
end

Stop All (Game Over)

when I receive [game-over v]
stop [all v]

---

Loop Termination Best Practices

Practice	Why
Always have exit condition	forever must have stop or broadcast [stop]
Use stop [this script]	Prefer over stop [all]
Clean up before stop	hide, delete this clone, stop sounds
Avoid stop [all] in libraries	Kills everything including UI

---

Boolean Combination — Complex Conditions! 🧠

Combining Booleans (And/Or/Not)

Operator	Block	True When...
AND	< > and < >	BOTH true
OR	< > or < >	AT LEAST ONE true
NOT	not < >	Flips true/false

---

Complex Boolean Combinations

Three Conditions (AND)

if < (score) > 100 > and < (lives) > 0 > and <not <touching [spike v]?>> then
    broadcast [bonus-level v]
end

Complex Condition

if < < (distance) < 50 > or <touching [player v]?> > and <not < (invincible) >> then
    broadcast [player-hit v]
end

De Morgan's Laws (Simplify!)

Original	Equivalent (Simplified)
not (A or B)	(not A) and (not B)
not (A and B)	(not A) or (not B)

---

Boolean Combination Examples

Complex Jump Condition

if <key [space] pressed?> and <touching [ground v]?> and <not < (in-air) >> then
    set [velocity-y v] to (15)
end

Enemy AI Decision

if < (distance to player) < 100 > and <not < (stunned) >> then
    if < (player-x) > (x position) > then
        set [velocity-x v] to (3)
    else
        set [velocity-x v] to (-3)
    end
end

---

Win Condition — Victory! 🏆

What Is a Win Condition?

Win condition = the specific goal that makes the player win the game!

Common Win Conditions

Type	Condition	Example
Score target	score > 1000	Collect 100 coins
All collected	length of [coins] = 0	Get all items
Reach location	x > 200 and y > 150	Reach exit
Defeat boss	boss-health = 0	Defeat final boss
Survive time	timer > 300	Survive 5 minutes
All enemies gone	length of [enemies] = 0	Clear room

---

Win Condition Implementation

forever
    // Check win conditions each frame
    if < (score) > 1000 > then
        broadcast [win v]
        stop [this script v]
    end

    if < (length of [coins v]) = 0 > then
        broadcast [win v]
        stop [this script v]
    end

    if < (boss-health) = 0 > then
        broadcast [win v]
        stop [this script v]
    end
end

---

Win Sequence

when I receive [win v]
stop [all v]
switch backdrop to [victory v]
play sound [fanfare v]
say [YOU WIN!] for 5 secs
wait 3 secs
show variable [final-score v]
wait 5 secs
broadcast [return-to-menu v]

---

Multiple Win Paths

Game Type	Win Conditions
Platformer	Reach flag, all coins, defeat boss
Puzzle	All pieces placed, all switches hit
Survival	Timer reaches target
RPG	Defeat final boss, complete main quest
Racing	Cross finish line first

---

Lose Condition — Game Over! 💀

What Is a Lose Condition?

Lose condition = specific situation where the player fails and game ends!

Common Lose Conditions

Type	Condition	Example
No lives	lives = 0	3 hits = game over
Time out	timer = 0	Didn't finish in time
Fall off world	y < -200	Fell in pit
Touch hazard	touching lava/spikes	Instant death
Fail objective	failed to protect NPC	Escort mission failed

---

Lose Condition Implementation

forever
    // Check lose conditions
    if < (lives) = 0 > then
        broadcast [game-over v]
        stop [this script v]
    end

    if < (timer) = 0 > then
        broadcast [game-over v]
        stop [this script v]
    end

    if < (y position) < -200 > then
        broadcast [game-over v]
        stop [this script v]
    end

    if <touching [lava v]?> then
        broadcast [game-over v]
        stop [this script v]
    end
end

---

Game Over Sequence

when I receive [game-over v]
stop [all v]
switch backdrop to [game-over v]
play sound [game-over-sound v]
say [GAME OVER] for 3 secs
wait 2 secs
say (join [Final Score: ] (score)) for 5 secs
wait 3 secs
broadcast [return-to-menu v]

---

Lose Condition Best Practices

Practice	Why
Clear feedback	Show WHY player lost
Quick restart	One click to try again
Progress saving	Don't lose all progress
Fair warning	"Low health!" before death
Learn from failure	Show what killed you

---

Inventory System — Player's Bag! 🎒

What Is an Inventory System?

Inventory = a list that holds items the player collects!

Inventory List Structure

inventory list:
[0] "health-potion"
[1] "iron-sword"
[2] "gold-key"
[3] "magic-scroll"

---

Inventory Operations

Operation	Code
Add item	add [potion] to [inventory v]
Remove item	delete (1) of [inventory v]
Use item	item (1) of [inventory v], then delete (1)
Check item	[potion] in [inventory v]?
Count items	length of [inventory v]
Show inventory	show list [inventory v]

---

Inventory Systems

Simple Inventory (Stack)

when I receive [pickup-item v]
add [item-name] to [inventory v]
say (join [Got: ] (item-name)) for 2 secs

Categorized Inventory

Categories: weapons, potions, keys, quest

when I receive [pickup v]
if < (item-type) = [weapon] > then
    add (item) to [weapons v]
else
    if < (item-type) = [potion] > then
        add (item) to [potions v]
    end
end

Weight/Slot Limit

if < (length of [inventory v]) < 20 > then
    add [item] to [inventory v]
else
    say [Inventory full!] for 2 secs
end

---

Inventory UI

when green flag clicked
hide list [inventory v]

when [i] key pressed
if < (showing-inventory) > then
    hide list [inventory v]
    set [showing-inventory v] to (false)
else
    show list [inventory v]
    set [showing-inventory v] to (true)
end

---

Summary

In this chapter, you learned:

• ✅ List Item Access — item (N) of [list] for specific items
• ✅ Delete From List — Remove items, trim lists
• ✅ List Contains — Check if item exists
• ✅ High Score List — Top scores with trimming
• ✅ Testing Strategies — Unit, integration, playtest, regression
• ✅ Debugging Strategies — Reproduce, isolate, hypothesize, test, fix
• ✅ Storytelling Flow — Three-act structure in games
• ✅ Synchronous Broadcast — broadcast and wait for coordination
• ✅ Broadcast Storm — Prevention and fixes
• ✅ Loop Termination — stop blocks for clean exits
• ✅ Boolean Combination — And/Or/Not for complex logic
• ✅ Win Condition — Score, collection, boss, survival, location
• ✅ Lose Condition — Lives, time, hazards, objectives
• ✅ Inventory System — Lists for items, categories, limits
• ✅ Testing Strategies — Unit, integration, playtest, edge cases
• ✅ Debugging Strategies — Reproduce, isolate, hypothesize, test, fix
• ✅ Storytelling Flow — Three-act game narrative
• ✅ Synchronous Broadcast — Coordinated multi-sprite starts
• ✅ Broadcast Storm — Rate limiting, cooldowns
• ✅ Loop Termination — Clean stop usage
• ✅ Boolean Combination — And/Or/Not for complex conditions

---

Key Terms to Remember

Term	Definition
List Item Access	item (N) of [list] — get specific value
Delete From List	Remove item at position
List Contains	Boolean check for item existence
High Score List	Sorted top scores list
Testing Strategies	Systematic bug-finding approaches
Debugging Strategies	Reproduce, isolate, hypothesize, test, fix
Storytelling Flow	Narrative structure in gameplay
Synchronous Broadcast	broadcast and wait coordination
Broadcast Storm	Message overload, prevention methods
Loop Termination	stop this script/all/other scripts
Boolean Combination	And/Or/Not for complex conditions
Win Condition	Goal that ends game in victory
Lose Condition	Condition that ends game in defeat
Inventory System	List-based item management
List Item Access	Getting specific list values
Delete From List	Removing items from collections
List Contains	Boolean membership check
High Score List	Persistent top scores
Testing Strategies	Quality assurance methodologies
Debugging Strategies	Systematic bug fixing
Storytelling Flow	Narrative pacing in games
Synchronous Broadcast	Coordinated multi-sprite messaging
Broadcast Storm	Message flooding prevention
Loop Termination	Clean script exit patterns
Boolean Combination	Compound logical conditions

---

Try It Yourself! 🎯

Challenge 1: Build a complete platformer with win (reach flag) and lose (3 lives) conditions

Challenge 2: Create an inventory system with categories (weapons, potions, keys)

Challenge 3: Implement high score list that saves top 10 scores

Challenge 4: Write test cases for your movement, collision, and scoring systems

Challenge 5: Debug a broken script using say to watch variable values

Challenge 6: Design a game story with 3 acts and implement with broadcasts

Challenge 7: Create a broadcast system for level loading without storms

Challenge 8: Design complex boolean conditions for enemy AI decisions

Challenge 9: Implement multiple win/lose conditions in one game

Challenge 10: Build a complete playable game with all mechanics learned!

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What's Next?

In Chapter 11, you'll master the Design Process and Capstone Project — the complete creative journey from idea to polished game, including planning, iteration, testing, polishing, and sharing your masterpiece!

→ Next Chapter: Design Process and Capstone Project