1

👾

The Enemy Class

Patrolling walkers built like the Player

Active

🎯

Goal for this step

Add an Enemy class with patrol movement, stored in a vector.

1Enemy mirrors Player: shape, vx, plus minX/maxX patrol bounds and an alive flag.
2Its update: move by vx·dt; flip vx at the bounds.
3A constructor taking (x, y, minX, maxX) makes placing them one-liners.
4Two enemies to start: one on the ground, one patrolling a ledge. Draw red.

platformer.cpp

class Enemy {
public:
    sf::RectangleShape shape;
    float vx = 120;
    float minX, maxX;
    bool alive = true;

    Enemy(float x, float y, float lo, float hi)
            : minX(lo), maxX(hi) {
        shape.setSize(sf::Vector2f(30, 24));
        shape.setPosition(x, y);
        shape.setFillColor(sf::Color(248, 113, 113));
    }

    void update(float dt) {
        shape.move(vx * dt, 0);
        float x = shape.getPosition().x;
        if (x < minX || x > maxX) vx = -vx;
    }
};

std::vector<Enemy> enemies;
enemies.emplace_back(390, 236, 380, 500);
enemies.emplace_back(60, 416, 40, 700);

✏️

Fill in the Blanks

+15 XP

The constructor line ": minX(lo), maxX(hi)" is an initialiser . Enemies are stored with emplace_back just like were in Episode 3.

🧠

Knowledge Check

+15 XP

Enemy and Player share the shape+velocity+update pattern. In bigger games this becomes…

ACopy-paste forever

BA shared base class (inheritance), Entity with Player and Enemy deriving from it

CA single giant class

2

🥾

Stomp or Suffer

Fall on heads to kill; touch sides to die

Locked

🎯

Goal for this step

Implement the stomp with the falling-from-above test.

1For each living enemy intersecting the player: falling AND bottom near their top → stomp (alive = false, bounce vy = -350, +score).
2Otherwise → death: respawn (checkpoints next step).
3Skip dead enemies everywhere (alive flag, Episode 3 pattern).
4The bounce chains stomps, line your two enemies up and try a double!

platformer.cpp

for (auto& en : enemies) {
    if (!en.alive) continue;
    if (pb.intersects(en.shape.getGlobalBounds())) {
        float enTop = en.shape.getPosition().y;
        if (player.vy > 0
                && pb.top + pb.height - player.vy * dt <= enTop + 10) {
            en.alive = false;
            player.vy = -350;      // bounce!
            score += 50;
        } else {
            respawn(player);
        }
    }
}

⌨️

Code Challenge

+20 XP

Squash the enemy and rebound:

platformer.cpp

en.alive = ;
player.vy = ;
score += 50;

💡 Hint: The enemy stops existing; the player bounces upward with a negative vertical velocity.

🧠

Knowledge Check

+15 XP

The stomp test reuses which platformer check?

AThe coin pickup

BLanding-from-above, the same "falling onto a top surface" logic aimed at an enemy

CThe wall clamp

3

🎥

The sf::View Camera

SFML’s built-in camera, three lines of scrolling

Locked

🎯

Goal for this step

Follow the player through a 2400 px level using sf::View.

1SFML has a real camera class: sf::View. Centre it on the player, clamped to the level, then window.setView(view).
2THAT IS IT, no offsetting of draw calls (remember doing that by hand in Python? Engines do this for you).
3Clamp centre x between 400 and levelWidth − 400 so the view never shows past the edges.
4For screen-fixed HUD: switch back with window.setView(window.getDefaultView()) before drawing text.

platformer.cpp

const float LEVEL_W = 2400.f;
sf::View view(sf::FloatRect(0, 0, 800, 480));

// each frame:
float cx = player.shape.getPosition().x + 17;
cx = std::max(400.f, std::min(LEVEL_W - 400.f, cx));
view.setCenter(cx, 240);
window.setView(view);

// ... draw world ...
window.setView(window.getDefaultView());
window.draw(scoreText);          // HUD stays put

✏️

Fill in the Blanks

+15 XP

The camera is an sf:: centred on the player. Before drawing the HUD we restore the view so text stays fixed on screen.

🧠

Knowledge Check

+15 XP

In Python you subtracted cam_x from every draw call. sf::View replaces that by…

ADrawing twice

BTransforming ALL drawing through the view automatically, the engine does the offsetting

CMoving the window

4

⚠️

Spikes & Checkpoints

Hazards, flags and one shared respawn function

Locked

🎯

Goal for this step

Add deadly spikes and fair checkpoint respawns.

1Spikes: vector of FloatRects on the floor; intersecting one calls respawn().
2Checkpoints: flag rects that update a respawnPoint Vector2f when touched.
3One respawn(player) function used by spikes, enemies and pits, single source of truth.
4Place checkpoints before hard sections. Draw spikes as red triangles (sf::ConvexShape), flags teal.

platformer.cpp

sf::Vector2f respawnPoint(100, 380);

void respawn(Player& p) {
    p.shape.setPosition(respawnPoint);
    p.vx = 0; p.vy = 0;
}

for (auto& cp : checkpoints)
    if (pb.intersects(cp))
        respawnPoint = { cp.left, cp.top - 44 };

for (auto& sp : spikes)
    if (pb.intersects(sp))
        respawn(player);

if (player.shape.getPosition().y > 480)   // pit
    respawn(player);

⌨️

Code Challenge

+20 XP

Update the respawn point at a checkpoint:

platformer.cpp

if (pb.intersects(cp))
    respawnPoint = { cp.left, cp.top -  };

💡 Hint: Spawn standing ON the flag: its top minus the player height.

🧠

Knowledge Check

+15 XP

Every death path calls one respawn() function. When you later add fall damage or a death sound, you edit…

AEvery collision block

BExactly one function, that is why shared paths matter

CThe Enemy class

5

🗺️

Levels as Structs

Bundle a whole level into one loadable object

Locked

🎯

Goal for this step

Define levels as data structs and swap between them.

1A struct Level holds: platforms, enemies (as spawn data), spikes, checkpoints, door, width.
2A makeLevel(int n) function returns the struct for level n, pure data, no logic.
3Loading = copying the struct’s contents into the live vectors and resetting the player.
4Reaching the door loads n+1; after the last, the champion screen. Your Ep 4 game is now a multi-level product.

platformer.cpp

struct Level {
    std::vector<sf::FloatRect> platforms, spikes, checkpoints;
    std::vector<Enemy> enemies;
    sf::FloatRect door;
    float width;
};

Level makeLevel(int n) {
    if (n == 0) {
        Level L;
        L.width = 2400;
        L.platforms = { {0,440,2400,40}, {150,340,140,16} /* ... */ };
        L.enemies.emplace_back(390, 236, 380, 500);
        L.spikes = { {760, 424, 40, 16} };
        L.checkpoints = { {1000, 380, 12, 60} };
        L.door = {2320, 380, 30, 60};
        return L;
    }
    // n == 1 ...
}

✏️

Fill in the Blanks

+15 XP

A Level bundles every vector one level needs. The function (n) returns pure data, building levels becomes filling in lists.

🧠

Knowledge Check

+15 XP

Separating level DATA from game LOGIC means…

ALevels run faster

BNew levels need zero new logic, and eventually data can come from files or a level editor

CThe compiler optimises structs

6

🏁

Polish & Ship

Death counter, timer, and the champion screen

Locked

🎯

Goal for this step

Add the finishing touches and complete your C++ platformer.

1Track deaths and a speedrun timer (one sf::Clock started at level 1), show both on the champion screen.
2Squash animation: dead enemies flatten (setScale(1, 0.3)) for 0.3 s before vanishing.
3Balance: walk each level; every death should feel like YOUR fault. Adjust spike placement until it does.
4Compile, play, hand the keyboard to someone. Watching a playtester is a developer rite of passage. 🏆

platformer.cpp

int deaths = 0;                 // ++ inside respawn()
sf::Clock runTimer;             // started at first level load

// champion screen:
int secs = (int)runTimer.getElapsedTime().asSeconds();
championText.setString(
    "CHAMPION!\nTime: " + std::to_string(secs / 60) + "m "
    + std::to_string(secs % 60) + "s\nDeaths: "
    + std::to_string(deaths));

⌨️

Code Challenge

+20 XP

Format the speedrun time from total seconds:

platformer.cpp

std::to_string(secs  60) + "m "
+ std::to_string(secs  60) + "s"

💡 Hint: Whole-number division gives minutes; the remainder operator gives leftover seconds.

🧠

Knowledge Check

+15 XP

A death counter and timer on the win screen add…

ALag

BReplay value, beat your time, deathless runs. Numbers players can chase for free

CCompile warnings

Full Game!Platformer Part 2

Full Game!
Platformer Part 2