Tutorials · Crypt Knight · Chapter 11

The Crypt

What the Crypt is

A scene made from the Gate

1. In Assets, open scenes, right-click gate.ron and choose Duplicate. Right-click the copy, gate-copy.ron, choose Rename, type crypt.ron, and press Enter.
2. Double-click crypt.ron to open it. In the Hierarchy, select the root, Gate, and rename it Crypt in the Inspector.
3. Select sky, then Ctrl-click mountains, forest, town, sign_walk, sign_jump, sign_high, sign_drop, sign_spikes, spikes and relic, and press Delete. The Crypt has no town to look at, and no spikes, tablets or relic of the Gate’s. Keep sign_air: it becomes the sword’s sign below.
4. Also delete safe_step, safe_ledge, safe_lower, safe_after_pit and safe_far. Keep pit, safe_start and the rest: the camera, ground, knight, bounds, hud and exit.

The Crypt’s floor plan

1. In Assets, open art, right-click gothic-castle-tileset.tilemap and choose Duplicate. Right-click the copy, gothic-castle-tileset-copy.tilemap, choose Rename, type crypt.tilemap, and press Enter.
2. Select ground in the Crypt’s Hierarchy, and drag art/crypt.tilemap onto the Tilemap slot of its TileMapComponent. Open the Tilemap tab, and turn on Paint mode. It still holds the Gate.
3. Choose the Erase tool, and set its Size to 16. Zoom out in the Viewport until the whole level, 102 cells across, shows. Under Layers, click back, and drag from cell (0, 6) to cell (101, 6): a brush 16 wide and tall, along the middle of the level, takes every row of it. Do the same on ground, and on ledges. The Viewport shows an empty level.

Safe ground and a pit

1. Select pit. Set its Position to 688 and 248, and its Area’s Shape Size to 96 and 32. The skull is over this pit.
2. Select safe_start, rename it safe_1, and set its Position and Size from the table below. Right-click it and choose Duplicate four times, and rename and set each of the copies.
3. Press Ctrl+S.

Three creatures from their strips

1. Double-click art/hell-hound-walk.png in Assets. The Sprite sheet tab opens on it. Under Grid, set Cell to 64 and 32. Drag across the whole top row, cell 0, 0 to cell 11, 0: Selected 12 x 1.
2. Under Clips, press From selection. Name the clip walk, set 12 fps and Loop, and press Generate 1. A file, art/hell-hound-walk.anim, appears beside the picture.
3. Double-click art/wolf-runing-cycle.png. Set Cell to 56 and 32, drag from cell 0, 0 to cell 3, 0: Selected 4 x 1. From selection, name run, 10 fps, Loop, Generate 1. A file, art/wolf-runing-cycle.anim.
4. Double-click art/fire-skull.png. Set Cell to 96 and 112, drag from cell 0, 0 to cell 7, 0: Selected 8 x 1. From selection, name burn, 10 fps, Loop, Generate 1. A file, art/fire-skull.anim.

A hound that patrols

1. In Assets, press Create, choose New script, type patrol, and press Enter.
2. In the Code tab’s Scripts list, click patrol.rgs, replace everything in it with the script below, and press Ctrl+S.

/// A patroller: walks back and forth, turning after `distance` or at a wall,
/// and faces the way it walks. Its art faces left.
component Patrol : Body {
    /// How fast it walks.
    #[suffix("u/s")]
    speed: f32 = 40.0,
    /// How far it walks before it turns.
    #[suffix("u")]
    distance: f32 = 128.0,
    /// The way it walks: -1 for left, 1 for right.
    way: f32 = 1.0,
    /// How far it has walked since it last turned.
    #[hidden]
    walked: f32 = 0.0,

    fn loop(dt: f32) {
        walked += speed * dt;
        if walked >= distance {
            way = -way;
            walked = 0.0;
        }
        set_number("CharacterBodyComponent", "velocity.x", way * speed);
        // Drawn facing left, so mirrored to walk right.
        set_flag("SpriteComponent", "flip.x", way > 0.0);
    }

    fn on_hit_wall() {
        way = -way;
        walked = 0.0;
    }
}

component Patrol : Body

A Body base: the script may have the body’s hooks, such as on_hit_wall, which runs when the body is stopped moving sideways. It is the script that sets the body’s speed: a body driven by a script keeps whatever its script last gave it.

walked and distance

A patroller counts how far it has gone, speed units a second times dt, in walked, and turns when it reaches distance: way flips from 1 to -1 and back, and walked starts again. A hound with a wall in front of it turns at once, in on_hit_wall, with the same two lines.

flip.x

The art faces left, so flip.x is on while the hound walks right, as the knight’s is off. The first hound, set way to 1, starts walking right.

1. Click the Viewport tab. Select Crypt, press + Add node, choose Character, and rename it hound_1. Set its Position to 400 and 160, under Groups type enemy and press Enter.
2. Remove its Shape with the bin icon at the right of the ShapeComponent header.
3. In its CharacterBodyComponent, set Size to 32 and 22, Driven By to Script, Gravity to 900 and Terminal Velocity to 400. Leave the rest.
4. Press Add component and choose SpriteComponent: set Texture by dragging art/hell-hound-walk.png onto it, Size to 64 and 32, Anchor to 0.5 and 1, and Sort Layer to 4.
5. Press Add component and choose AnimatedSpriteComponent: drag art/hell-hound-walk.anim onto Animations, set Clip to walk, and leave Frame Size unticked: the Sprite’s own size, 64 by 32, is the frame’s.
6. Press Add component and choose AreaComponent. In its Shape, set Size to 28 and 18, Offset to 0 and -9, and its own Layer to 1, and untick 0 in its Mask: it is an enemy, and enemies are on layer 1 and look for nothing, as hazards do.
7. Press Add component and choose Patrol. Leave its Speed at 40, Distance at 128 and Way at 1.
8. Right-click hound_1 and choose Duplicate. Rename the copy hound_2, set its Position to 1300 and 160, and its Patrol’s Distance to 112.
9. Press Ctrl+S.

A skull that bobs

1. In Assets, press Create, choose New script, type bob, and press Enter. In the Code tab, replace everything in bob.rgs with the script below, and press Ctrl+S.

/// Bobs up and down for ever: `rise` units up and back, `period` seconds each
/// way.
component Bob {
    /// How far up it rises.
    #[suffix("u")]
    rise: f32 = 72.0,
    /// Seconds to rise, and as long to sink back.
    #[suffix("s")]
    period: f32 = 1.2,

    fn on_create() {
        // Up is toward negative y.
        pulse_by(vec2(0.0, -rise), period, .InOutSine);
    }
}

1. Click the Viewport tab. Select Crypt, press + Add node, choose Sprite, and rename it skull. Set its Position to 688 and 176, the middle of the pit, and under Groups type enemy.
2. Drag art/fire-skull.png onto its Sprite’s Texture, and set Size to 96 and 112, Anchor to 0.5 and 0.5 and Sort Layer to 4.
3. Press Add component and choose AnimatedSpriteComponent: drag art/fire-skull.anim onto Animations, and set Clip to burn.
4. Press Add component and choose AreaComponent. In its Shape, set Size to 28 and 30, and Offset to 0 and 8, the bright core of the skull and not its flames; set its own Layer to 1, and untick 0 in its Mask.
5. Press Add component and choose Bob. Leave its Rise at 72 and Period at 1.2.
6. Press Ctrl+S.

A wolf that dashes

1. In Assets, press Create, choose New script, type dash, and press Enter. In the Code tab, replace everything in dash.rgs with the script below, and press Ctrl+S.

/// A dasher: runs one way until a wall stops it, waits there, then runs back.
/// Its art faces right.
component Dash : Body {
    /// How fast it runs.
    #[suffix("u/s")]
    speed: f32 = 160.0,
    /// Seconds it waits at each wall.
    #[suffix("s")]
    rest: f32 = 1.0,
    /// The way it runs: -1 for left, 1 for right.
    way: f32 = 1.0,
    /// Seconds of waiting left.
    #[hidden]
    waiting: f32 = 0.0,

    fn loop(dt: f32) {
        if waiting > 0.0 {
            waiting -= dt;
            set_number("CharacterBodyComponent", "velocity.x", 0.0);
        } else {
            set_number("CharacterBodyComponent", "velocity.x", way * speed);
        }
        // Its legs stop while it waits.
        set_flag("AnimatedSpriteComponent", "playing", waiting <= 0.0);
        set_flag("SpriteComponent", "flip.x", way < 0.0);
    }

    fn on_hit_wall() {
        way = -way;
        waiting = rest;
    }
}

1. Click the Viewport tab. Select Crypt, press + Add node, choose Character, and rename it wolf. Set its Position to 904 and 192, the floor of the trench, and under Groups type enemy. Remove its Shape.
2. In its Character Body, set Size to 36 and 18, Driven By to Script, Gravity to 900 and Terminal Velocity to 400.
3. Add a SpriteComponent: drag art/wolf-runing-cycle.png onto its Texture, Size 56 and 32, Anchor 0.5 and 1, Sort Layer 4.
4. Add an AnimatedSpriteComponent: drag art/wolf-runing-cycle.anim onto Animations, Clip run.
5. Add an AreaComponent: Shape Size 32 and 14, Offset 0 and -7, its own Layer 1, and 0 unticked in its Mask.
6. Add Dash, and leave its Speed at 160 and Rest at 1.
7. Press Ctrl+S.

The knight meets an enemy

/// The knight: runs where `move` points, jumps on `jump`, jumps lower when
/// `jump` is let go early, drops through a ledge when `down` is held as it
/// jumps, jumps once more in the air once the relic is taken, faces the way it
/// last moved, and shows the clip for what it is doing. It keeps where it last
/// stood on safe ground. A spike or a pit costs it a heart and puts it back
/// there; an enemy costs it a heart and hops it back. A hurt shakes the camera
/// and blinks the knight, and nothing can hurt it while it blinks. A heart it
/// picks up heals one. With no hearts left, the level is lost.

    /// How long an enemy's hurt takes the knight's steering away while it hops
    /// back.
    #[suffix("s")]
    hop_time: f32 = 0.25,
    /// Seconds of the hop still to run.
    #[hidden]
    hopping: f32 = 0.0,

    fn loop(dt: f32) {
        // A heart picked up says "heal" to the group "knight", heard a step
        // later.
        if heard("heal") {
            hearts = min(hearts + 1.0, 5.0);
            keep_number("hearts", hearts);
        }
        // One more jump in the air once the relic is taken: double_jump is
        // kept as 0 or 1.
        set_number("CharacterBodyComponent", "air_jumps", kept_number("double_jump", 0.0));
        let x = direction("move").x;
        if hopping > 0.0 {
            // Hopping back from a hurt: the hop keeps its own speed.
            hopping -= dt;
        } else {
            set_number("CharacterBodyComponent", "velocity.x", x * speed);
            let drop = pressed("jump") && held("down");
            set_flag("CharacterBodyComponent", "drop_through", drop);
            if pressed("jump") && !drop {
                jump();
            }
            if !held("jump") {
                cut_jump();
            }
            if x != 0.0 {
                facing = x;
            }
        }

    /// When the knight's Area meets another: a spike, a pit or an enemy costs
    /// a heart.
    fn on_enter(other: NodeId) {
        let hazard = in_group(other, "hazard");
        if hazard || in_group(other, "enemy") {
            hearts -= 1.0;
            keep_number("hearts", hearts);
            if hearts <= 0.0 {
                fail();
            } else {
                if hazard {
                    move_to(kept_point("safe", position()));
                    set_point("CharacterBodyComponent", "velocity", vec2(0.0, 0.0));
                } else {
                    // Up, and back the opposite way to the way it faces.
                    set_point("CharacterBodyComponent", "velocity", vec2(-facing * 90.0, -160.0));
                    hopping = hop_time;
                }
                // The camera's node is in the group "camera".
                emit_to("camera", "shake");
                pulse_colour("SpriteComponent", "color", vec4(1.0, 1.0, 1.0, 0.25), 0.08, .Linear);
                // A hook that is waiting ignores every call until it finishes,
                // so while this one waits, nothing can hurt the knight.
                await wait(blink_time);
                // Setting the colour ends the blink.
                set_colour("SpriteComponent", "color", vec4(1.0, 1.0, 1.0, 1.0));
            }
        }
    }

let hazard

A local, true when the thing met is in the group hazard. A hazard puts him back on safe ground, as in chapter 9; anything else that costs a heart, an enemy, hops him instead.

velocity of -facing * 90 and -160

The hop: 90 units a second away from the way he faces, and 160 up. set_point writes a vector into the body’s velocity. For the 0.25 seconds of hopping, loop leaves his sideways speed alone, so the hop carries him instead of the keys.

Why away from where he faces

A script cannot read another node’s position, so the knight cannot tell which side an enemy struck him from. Throwing him back away from the way he faces is right for a hit from the front, which is nearly every hit; a hit from behind throws him toward the enemy, once.

heard "heal" and min

A heart he picks up, below, tells the group knight to "heal"; the knight hears it a step later and adds a heart, never above five.

Two hearts to pick up

1. In Assets, press Create, choose New script, type heart, and press Enter. In the Code tab, replace everything in heart.rgs with the script below, and press Ctrl+S.

/// A heart lying in the crypt: it bobs, and the knight takes it by walking
/// into it, which heals one heart. Then it is gone.
component Heart : Area {
    fn on_create() {
        pulse_by(vec2(0.0, -3.0), 0.5, .InOutSine);
    }

    fn on_enter(other: NodeId) {
        if in_group(other, "knight") {
            // The knight is in the group "knight", and hears this a step
            // later.
            emit_to("knight", "heal");
            hide();
        }
    }
}

1. Click the Viewport tab. Select Crypt, press + Add node, choose Shape, and rename it heart_pickup_1. Set its Position to 776 and 148, and its Rotation to 45.
2. In its Shape, keep Kind on Rectangle, set Size to 7 and 7, Anchor to 0.5 and 0.5, Outline to 0, Color to 0.6, 0.02, 0.06 with an alpha of 1, and Sort Layer to 6: a small red diamond, the colour of the HUD’s.
3. Add an AreaComponent: Shape Size 12 and 12. Leave its Layer and Mask: it is on layer 0 and looks for the knight, who is there.
4. Add Heart.
5. Right-click heart_pickup_1 and choose Duplicate. Rename the copy heart_pickup_2, and set its Position to 992 and 116: over the second ledge.
6. Press Ctrl+S.

The sword on its altar

1. Select Crypt, press + Add node, choose Shape, and rename it sword. Set its Position to 1512 and 118.
2. In its Shape, keep Kind on Rectangle, set Size to 3 and 16, Anchor to 0.5 and 0.5, Outline to 0, Color to 0.85, 0.88, 0.92 with an alpha of 1, and Sort Layer to 6: a thin bar, standing on its end.
3. Add an AreaComponent: Shape Size 16 and 48, Offset 0 and 18.
4. Add Relic, and set its Power to sword.
5. Select sign_air, the Gate’s sign you kept, and rename it sign_sword. Set its Position to 1512 and 98, the Text of its World Text to J or X to strike., the Size of its Shape to 110 and 13, and its Area’s Offset to 0 and 34: 17 characters make 110, and the Area is lower, to reach the floor.
6. Press Ctrl+S.

The Crypt on the list

1. Click the Levels tab. Type The Crypt into the box in the panel’s bar and press Add level.
2. With its row selected, press Scene and choose crypt.ron.
3. Drag abandoned_castle_music_-_starninjas_6.ogg from audio in Assets onto the Music button of its row: the same loop as The Gate’s.

Check it works