Physics games

The Physics template

File → New Project → Physics is a slingshot game to play straight away, and to take apart: three levels of wood, glass and stone with green grubs inside to knock out, and a menu to pick them from. It’s all no-code components (a Slingshot, Breakable blocks, a Level Goal, Stars, counters and panels), its pictures and sounds made by Griff.

• The menu (Main) has a card for each level (Timber, Glasshouse and Stone Keep) with the best stars and score it’s been won with. The first is open from the start, and each of the others once the one before has been won (its button Needs Saved the level before’s stars). Arrows and Enter pick one, or click or tap it.
• A level (Level1 to Level3) has a slingshot on a mound of rock on the left with its birds waiting in a row behind it (the last level’s last shot is a heavy boulder, for stone), and the towers on the right: posts and planks, square blocks and triangular roofs, on the ground or on rock. Drag the bird back with the mouse (or a finger) and let go, or pull with the arrows (or a stick) and let go with Space (or A); the dotted line shows where it’ll fly and the camera follows it, staying inside the level. Wood cracks and splits, glass shatters, stone crumbles, each with its own sound and its points rising where it broke, and a grub pops in a puff of green (it has a Health for three knocks’ worth, flashing as it’s hurt). In the third level a stone weight hangs on a Rope from a beam across two rocks, over a grub: break the beam and down it comes.
• Every block’s material is a row of the Materials table (Tables/Materials.table): its Strength, Min Hit, Points, its pictures (a plank, a block and a wedge of it) and its break and hit sounds, set on each block by a Table Values. Change a cell and every block of that material changes, while the game runs too. A block’s weight is its material’s for its size.
• The HUD shows the level, the shots and grubs left (texts reading the slingshot’s Shots Left and the level goal’s Targets Left), the score (a Counter of every piece’s Break Message) and the best, and a Retry button (R) that the arrow keys never pick and Space and A never press, since they’re the slingshot’s.
• Winning: once the last grub is down and things have settled, each bird left scores 10,000, counted one by one, and the Complete panel opens with the stars the score earned popping in one after another, the score and the best, and Next, Again and Levels. Running out of birds with grubs standing opens the Failed panel: Try Again or Levels. Esc (or Start) pauses.

The best stars and score of each level are kept in the save data (Level1.Stars, Level1.Best), from one run to the next, in the browser too. The scenes it plays the same every time: the same pulls topple the towers the same way, to the bit, and a rewind in the middle of a collapse plays it out again just as it went.

A level to knock down

Entity → Genres → Physics Games → Slingshot puts a Slingshot on the left with three shots waiting behind it, and Entity → Genres → Physics Games → Tower a little tower on the right: two storeys of wooden posts and planks, a pane of glass and a stone slab, with a green target inside. Play, pull the slingshot’s pouch back with the mouse and let go: the shot flies off the other way, the camera follows it, and whatever it hits hard enough cracks and breaks, the tower tumbling down as its pieces give way. Each piece broken adds its points to the score along the top. A scene with nothing solid to stand things on gets the ground too, and a camera with no Follow gets one following the slingshot. All of it works from the Inspector, with no code.

Entity → Add Breakable makes whatever’s selected break on hard knocks: it gets a Breakable, a Body that rotates (so it tumbles and topples) and a box collider the size of its sprite if it has no collider.

Slingshots

A Slingshot draws itself: a forked frame in its Color with elastic bands in its Band Color, the prongs Fork Width apart, and a pouch at its Pouch (from its position, its foot). Its shots are the bodies inside it, in order: the first sits in the pouch and the rest wait in a row behind its foot, held still and out of the way (nothing bumps into them, nor the shot in the pouch into them as it’s pulled back past them). Once they’re gone it makes copies of its Shot prefab (a bird, a boulder), Shots of them. A shot is any body: give it Rotates and it tumbles and rolls as it lands, a Mass for how hard it hits, Bounciness to bounce.

• With the mouse (or a finger on a touch screen): press within Grab Radius of the pouch, drag it back and let go. The further it’s pulled (up to Max Pull), the faster the shot leaves, the other way: at its Power (world units a second) all the way back. Pulled less than Min Pull, it’s let back without launching. It can’t be pulled so low the shot would go into the ground under its foot.
• With the keys or a gamepad: the arrows (A, D, W, S, the d-pad or the stick) pull the pouch about at Pull Speed, the Launch Action (Jump: Space or A) lets go and the Cancel Action (Dash: Shift or B) lets it back.

While it’s pulled a dotted line shows where the shot will go for Preview seconds, in Preview Color: the path the game will fly it on, step by step, so the shot passes through each dot (it doesn’t see what’s in the way). With Camera Follows, the camera’s Follow follows each shot as it flies and goes back to what it followed once the shot has come to rest. Auto Load loads the next shot Load Delay seconds after the last has come to rest (or gone, or flown for ten seconds: off the edge of the world), and the first as the game starts.

Its actions, for a Trigger, a wire or a script: Load (the next shot into the pouch now) and Launch (what’s in the pouch, as it’s pulled, or with nobody pulling it at its Default Pull: a catapult a trigger fires on the beat, or a cannon a wire sets off). Its outputs: Shots Left (inside it, the loaded one too, and copies of its prefab still to come), Stretch (how far it’s pulled, 0 to 1) and Out Of Shots, which turns on once it has none left and the last has come to rest: wire it to a panel that says the level’s lost, or count it with a Counter. It plays its Stretch Sound as it’s first pulled and its Launch Sound as it lets go, and sends its Launch Message (with the shot) and Out Of Shots Message.

Breakable things

A Breakable breaks when it’s hit hard enough. A hit is as hard as the push it takes to stop the two coming together, their speed towards each other times their weights shared: a crate of Mass 1 landing on the floor at 5 units a second hits 5, a heavy ball hits harder than a light one, and a fast one harder than a slow one. Hits softer than its Min Hit do nothing at all, so resting in a tall tower, nudges and landing gently don’t wear it down; harder ones add up in its Damage, and once that reaches its Strength it breaks. Hits come from anything: a shot, a falling block, the floor it’s knocked onto, another piece of the tower, so one thing breaking can bring down the next.

As its damage builds up it cracks: its Stages of cracking (3), one more for each share of its Strength, drawn over it in Crack Color, the same cracks every time. With a sprite sheet (a Sprite with Columns or Rows) its frames are the stages instead, from whole at frame 0 to most cracked.

As it breaks it splits into pieces (Split: 2 halves a plank and quarters a crate, 3 makes nine of a crate), each a part of its sprite (cut from its picture), moving and turning as it was, flying apart a little and fading away after Pieces Last seconds; the pieces knock into things too. With Split 0 it vanishes. Either way a puff of Dust in its color bursts out, or its Effect prefab (an explosion, a score popup) in its place, and its Sound plays; a hit that damages without breaking plays its Hit Sound. Remove takes it away; untick it to leave it turned off instead, with its Broken output on, until its Repair action brings it back (a wall a wire mends).

It sends its Break Message as it breaks, carrying its Points (a Counter adds them up into a score) or, with none, the entity (a Counter counts one), and its Damage Message with each hit’s damage. With Show Points its points rise from where it broke and fade, in its Points Color: what knocking it out scored. Its actions: Break, Damage (as a hit that hard would) and Repair. Its outputs: Damage (out of its Strength, for a Bar) and Broken.

Materials from a table

Wood, glass and stone are rows of a table: make a Materials table with a row for each and columns named like the properties they set (Strength, Min Hit, Mass for the body, Tint for the sprite as #8E929C, Sound, Split), and give each block a Table Values on it with its Row (Glass). Balancing the table while the game runs changes every block of that material at once. Strengths to start from: glass 4 (Min Hit 1.5, light), wood 12 (Min Hit 3), stone 40 (Min Hit 6, heavy).

Targets

A target to knock out (a pig in a tower) is just something breakable: a low Strength (3) and a high Points. Or give it a Health as well: each hit that counts takes its damage off that too (so its health bar, flash and Hurt Sound go with it), and it breaks as its health dies (Strength 0 leaves it to its Health; give the Health an Invincible Time of 0 so every hit counts). A Counter of the Break Messages keeps the score; a Level Goal says when the level’s won or lost (below).

Winning a level

A Level Goal (on an entity of its own, Level) is what a level is for: knock out every one of its Targets (everything called that, Target; a Breakable is gone once it’s broken, anything else once it’s removed or turned off, so they can be a platformer’s enemies too) before its Slingshot (by name; empty is the scene’s first) runs out of shots. It counts them as the game starts.

• Once the last is down it takes the slingshot’s controls away and waits Settle seconds (2) for things to settle, then counts a Shot Bonus (10,000) for each shot left, one after another, each taken from the slingshot with its Bonus Sound and its points rising where it was, adding them to its Score (a Counter, by name: Score). Then it gives the level its stars, one for winning, two from Two Stars points and three from Three Stars, plays its Win Sound and sends its Won Message (Level Complete, with the stars): a Panel with that Open Message says so.
• Out of shots with targets still standing (once the last shot has come to rest), it waits Settle seconds as well (a target knocked out meanwhile still counts, and wins it), then plays its Lose Sound and sends its Lost Message (Level Failed, with how many are left).
• With Save As (Level1) it keeps the best stars the level has been won with in the save data as Level1.Stars and the best score as Level1.Best, from one run to the next: a level select menu’s Stars show them, a Counter with Save Best As Level1.Best and the format Best: {1} shows the score, and the next level’s button Needs Saved Level1.Stars, opening once it’s won. A worse win keeps the best.

Its actions, for a trigger, a wire or a script: Win (now, counting the bonus) and Lose. Its outputs: Targets Left (out of how many there were), Stars, Won, Lost, Best Stars and Best Score, for texts (Grubs: {0} / {1}), bars and wires. Where the level has got to (playing, settling, counting the bonus, won or lost) is saved with the scene, so a rewind goes back into the middle of it.

Stars

Stars (Entity → UI → Stars) draws a row of stars, Count of them (3), so many filled: an output (Track Level and Output Stars, on the panel a won level opens), a number kept in the save data (Saved Level1.Stars, on a level select menu’s card), or its own Value. With a Delay they fill one after another, each popping in with its Sound, in real time, so they go on under a panel that pauses the game. It draws plump stars in its Color with a Rim, the empty ones in Empty Color, or its Image tinted so.

Pinball

The Pinball template

File → New Project → Pinball is Midnight Midway, a pinball table at a night carnival to play straight away and take apart, all of it the pinball pieces below and Griff’s no-code components, its pictures and sounds made by Griff.

• The title (Main) shows the best score, with Play (Enter) and Quit (Esc) and the controls.
• The table (Table) is played with three balls. Shoot from the plunger on the right up round the top; a full shot rings the bell hanging on a rope under the top right corner (250, and it swings) and drops through the top lanes. The three top lanes, M, I and D, light as the ball rolls through (100 each, the flippers moving the lit ones along); lighting all three scores 1,000 and raises the multiplier one step, up to 5x (the row of inserts over the flippers lights up to it), and every point after counts that many times over, until the ball’s lost. Under the lanes are three pop bumpers (100); up the left a bank of three drop targets (250 each, 1,000 for the set: knock them all down twice in a game and it’s an extra ball, once a game), with the orbit above them (250) up the left wall round the top; up the right the skyway, a channel beside the shooter lane with a ramp into it from below (500). Over the flippers are two slingshot kickers, an inlane each side back down to its flipper and an outlane outside it, straight down the drain.
• A ball lost within 8 seconds of being shot is saved, once: the shoot again light over the drain is lit while it would be, and a saved ball is served and shot again by itself. Nudge with N (or the up arrow); too many close together tilts the table, the flippers dropping and everything going dead until the ball drains.
• Down the left are the score, the best, which ball it is and the multiplier; the controls are on the right, and BALL SAVED, EXTRA BALL! and NEW BEST! pop up over the table as they happen. The last ball lost opens Game Over: the score, the best, “New best!” when it is one, and Play Again (Enter) or Title (Esc). Esc (or Start) pauses; a button still held from the pause menu (Space or A clicking Resume) doesn’t pull the plunger, nor B going back out nudge the table.

How it’s put together, with no code: the Score is a Counter of the Score message Multiply By the Multiplier counter, keeping its best as Pinball.Best (Save Best As) and sending New Best as the game beats it (a Sound Player plays a sting on it), with a Trigger for each set’s bonus (Lanes Lit and Targets Down, Do Add with the message’s number). The Multiplier is a counter of Lanes Lit, one a message (One Per Message), starting at 1 with a Max of 5, and a trigger sets it back to 1 on the drain’s Ball Lost. The Target Banks counter counts Targets Down and at 2 (Reaches) sends Extra Ball, which a trigger on the drain turns into its Extra Ball action. Each callout is a Spawner a trigger sets off, spawning a word that fades (a Lifetime); the multiplier’s inserts and the shoot-again light are Stars showing the multiplier’s Count and the drain’s Saving. Played again with the same buttons, a game ends with the same score to the last bit, and a rewind with the multiplier up plays on as it went; playing makes no garbage, but for writing the score’s new text and a ball’s comings and goings.

Tables and pieces

Entity → Genres → Physics Games → Pinball Table makes a whole little table to play straight away: walls round a playfield, a plunger in its lane on the right with the ball resting on it, two flippers over the drain, three pop bumpers, two slingshot kickers, three lanes along the top and a bank of three drop targets on the left, with the score and the ball shown beside it, pictures and sounds (in Assets/Pinball, to repaint and remake). The camera is moved and widened to see all of it. Play, hold Space (or the down arrow) and let go to shoot, flip with Left Shift or Z and Right Shift or / (a gamepad’s shoulders or triggers), and nudge with N (or the up arrow, or B). The pieces are on the same menu one at a time too: Flippers (a pair), Bumper, Kickers (a pair), Plunger (with a ball on it), Drop Targets (a bank of three) and Lanes (three). Everything is ordinary physics underneath: the ball is a body with a circle collider that rotates, the walls are colliders (slanted ones have a frozen body that rotates, so their box turns with them), and every piece works from the Inspector.

Flippers

A Flipper is a paddle on a Hinge Joint. While its button is held it swings up as fast as its Speed (2,000 degrees a second: up in a couple of hundredths of a second) and as hard as its Strength, to its hinge’s upper limit, and stays there, cradling the ball; let go and it drops back to the lower one. How far it swings is the hinge’s limits (drag the ends of the arc in the Scene view; a hinge with none is given its side’s, resting as it starts and swinging 55 degrees up). Its Side says which way it swings: a Left flipper points right and swings up anticlockwise, a Right one the other way. Its body rotates and is heavier than the ball (Mass 3 against the ball’s 1), so the ball comes off it hard and the same every time: the further along the paddle it is, the faster (about 40 units a second near the tip).

• Its Action is the input action that holds it up; empty, it’s Left Flipper or Right Flipper by its side, two of Griff’s own actions (rebind them in Game → Controls…).
• With Touch, the mouse or a finger held down on its side of the table’s flippers (left of the middle between them, for a left one) holds it up too: on a touch screen every finger counts, so a finger on each side holds both up (and one on the plunger pulls it meanwhile).
• A switch or a wire into its Power (Raised) holds it up, as do its Raise action (until Lower) and, for a moment, Flip: a flipper a Trigger, a wire or the beat flips. Its outputs: Up, and Flips (how many times it’s swung up). It plays its Sound and sends its Message as it swings up.

A fast ball doesn’t go through a flipper, swinging or not: the game works out where the two will meet within each step, and moves a fast body in parts small enough not to pass through anything.

Bumpers and kickers

A Bumper knocks whatever touches it away at its Strength (16 units a second), straight away from its middle, as it flashes its sprites in its Flash Color, pops bigger by its Pop, plays its Sound and sends its Message (Score) with its Points (100), for a Counter keeping the score. After a knock it rests for its Recover time. Give it a Direction (in its own space, turned with it) and it’s a slingshot kicker: only what touches its side facing that way is kicked, that way, so a ball rolling against its back does nothing. Layers limits what it knocks; untick On (or wire its Power) and it’s just a wall. Its Flash action lights it up without a ball, and its outputs are Hits and Lit (on for a moment after each). Its Direction has a compass with a middle for none (straight away from its middle), and with Distance handles out the Scene view draws it turned with the bumper.

The plunger

A Plunger is the tip the ball rests on at the bottom of its lane (give it a solid collider there; its position is the top of its tip). Hold its Action (Plunger: Space, the down arrow, the gamepad’s A) to pull it back, further the longer it’s held, all the way in Pull Time seconds, and let go: whatever rests on its tip is shot its Direction (up) at a speed from Min Power (a tap) to Power (all the way back). A pull starts with a press while the table’s being played, so a button still held from a menu (Space or A clicking a pause menu’s Resume) doesn’t pull it. With Analog, a gamepad’s right stick pulled down pulls it as far as it’s pushed, and letting the stick spring back shoots at the pull it had (let back slowly, it doesn’t shoot). The mouse or a finger held down within Grab Radius of its tip pulls it like the button. It draws itself, a knob on a rod in a spring that squeezes up as it’s pulled (Travel, Length, Width, Color, Spring Color), plays its Pull Sound and Launch Sound, and sends its Launch Message with the ball. Its Launch action shoots at full power with nobody pulling it (an auto-plunger, or a kickback a Trigger fires); its outputs are Pull, Loaded (a ball rests on it) and Launches.

Drop targets and lanes

A Target is something solid the ball hits: a hit harder than its Min Hit scores its Points with its Message and lights it (unlit targets are drawn darker); a drop target (Drops) falls out of the way as it’s hit, drawn faint, and the ball goes through where it was. A Lane is a trigger the ball rolls through (at least a ball’s width long): it scores and lights once each time a ball goes in. Targets and lanes come in sets, those inside the same entity: once every one of a set is lit, the set sends its Complete Message with its Complete Points (1,000), and Reset After seconds later they all come back up unlit, ready again. A lane with Flipper Changes moves the lit lanes of its set along each time a flipper of its table swings up (the left flipper to the left, the right to the right, round from the end), so the player lines the unlit one up with where the ball will go. Their actions are Light and Reset; their outputs Lit, Down and Hits (a target’s) and Lit and Passes (a lane’s).

The drain, ball saves and extra balls

A Drain is a trigger below the flippers. A ball that falls into it is lost: it’s taken off the table and Serve Delay seconds later put back on the Plunger (the one it names, or the nearest) as the next of its Balls, until the last is lost and the game’s over (its Game Over Message, GameOver, for a panel that says so). A ball lost within Ball Save seconds of being shot from the plunger is given back instead: served again and shot by itself, with its Save Message (once: shot again, it has no ball save of its own). While other balls are still on the table (multiball), a ball that drains just goes and no ball is lost; Within says which table’s balls it counts, by name. Its actions are Extra Ball (a ball more: a set of targets or a Counter’s Reach can award one) and Save Ball (a ball save of its Ball Save’s seconds); its outputs are Ball (which ball, out of its Balls), Balls Left, Game Over and Saving. The table’s Balls Counter shows which ball it is, counting the drain’s Ball output (“Ball {0} of {2}”).

Nudging and the tilt

A Tilt looks after a table: what’s inside the entity its Within names (or stands in its area), or the whole scene. Its Nudge Action (Nudge: N, the up arrow, the gamepad’s B) bumps the table: every ball on it gets a push of Nudge Strength its Nudge Direction (up the table), or that way and to the side while left or right is held, and the view shakes by its Shake. Each nudge adds one to its Danger, which falls back by one every Settle seconds: a nudge that takes it past one warns (its Warning Message, and “DANGER” over the table), and one that takes it past Warnings plus one tilts it (“TILT”, its Tilt Message). Tilted, the flippers drop and stay down and the bumpers, kickers, targets and lanes go dead until the ball drains (a Drain it covers puts it right), or its Reset action. Its actions are Nudge, Tilt and Reset; its outputs Danger, Tilted and Nudges.

Scoring

Every piece that scores sends a message with its points, Score by default, and a Counter whose Message is Score adds them up: the table’s Score on the camera. Give pieces their own messages to count them apart (a Counter of drop target hits whose Reach awards an extra ball), and wire outputs anywhere: a bumper’s Hits into a boss’s Bar, a set of lanes’ Complete Message into a door. A multiplier is a counter too: give the score’s Counter a Multiply By naming it, and everything scored counts that many times over (its Max caps it, and a Trigger’s Set puts it back as the ball drains); the Pinball template above does it all.

Mixing it with other games

Untick a slingshot’s Controllable (or Focus something else) and it ignores the mouse and keys while its actions still work, so a slingshot can sit in a platformer and take over the arrow keys only when the player walks up to it (see Mixing genres). Give it a Turn Taker naming its side and it’s pulled only on its side’s turn, each launch using one of the turn taker’s Actions: two slingshots taking turns at each other’s towers. Flippers, plungers and tilts have Controllable too, so a pinball table in another game answers to its buttons only while it has focus, and with a Turn Taker (on them or the table) they’re played only on their side’s turn: two players taking turns at one table. A bumper’s, a target’s or a lane’s Message carries its points, so a Trigger on a boss hearing it From that bumper does Damage: the boss loses health each time the ball hits it (see Four mixes, no code).

Rewinds and network games

Everything a slingshot, a breakable and a level goal know (what’s loaded and how far it’s pulled, how many it has made, the shot in flight, damage, what’s broken, where the level has got to) is saved with the scene, and a hit is worked out from the same physics every time, so a rewind replays a tower falling to the last bit, and so does playing it again. So is everything a pinball table knows (each flipper’s hinge and whether it’s up, the plunger’s pull, which targets and lanes are lit, the danger and the tilt, which ball it is and the one waiting to be served), so a game played again with the same buttons ends with the same score, and a rewind goes back into the middle of one. Playing makes no garbage, scoring included. In a network game the host runs the physics and the breaking, and the pieces and dust come to everyone; a player pulls a slingshot on their own screen (with its line), and their pull and let-go are sent to the host, which launches the shot. With the Multiplayer’s Teams, only the players on a slingshot’s Turn Taker side pull it. A pinball table is run by the host too: each player’s buttons, stick and mouse reach it, and it flips, shoots and nudges for them. A table nobody owns answers to every player (with Teams and a Turn Taker, those of its side), and one a player owns (their own table, made for them by the Multiplayer) to them alone.

Scripting

Physics tells scripts how hard things hit: Game.Physics.Impacts lists the last step’s hard knocks, both ways round (impact.Struck, impact.By, impact.Strength, impact.Point). A breakable’s Hit (with the damage and what hit it) and Broke events say what happened to it, and Stage how cracked it is; a slingshot’s Launched event hands over each shot, LoadedShot is the one in its pouch, and LaunchVelocity(pull) how fast a pull would launch one. A level goal’s Completed (with the stars) and Failed events say how a level ended, and StarsFor(score) what a score would earn. Pinball pieces have events too: a flipper’s Flipped, a bumper’s Knocked (with what it knocked), a plunger’s Launched (with the ball) and SpeedFor(pull), a target’s Hit, a lane’s Passed, a drain’s Drained (with the ball and whether it was saved) and a tilt’s Warned and TiltedOver.

public class Shockwave : Behavior
{
    // Whatever this hits hard is shoved away as well.
    protected override void Update()
    {
        var at = Entity.Transform.WorldPosition;
        foreach (var impact in Game.Physics.Impacts)
        {
            if (impact.By == Entity && impact.Strength > 5 && impact.Struck.GetComponent<Body>() is { } body)
                body.Velocity += Vector2.Normalize(impact.Point - new Vector2(at.X, at.Y)) * 4;
        }
    }
}