sgame

A minimalist (web) game development framework. Extracted from a (unreleased) closed source game I've been working on. Pretty early: seems pretty stable but options limited (e.g. assumes is always fullscreen canvas).

Uses Solandra for drawing.

Allows you to quickly make games without bitmap assets (everything is code).

Explicitly separates state updates (handled by the update function) and rendering. Though unlike some functional frameworks that were inspirations isn't pure. You typically mutate stuff directly (but you could easily drop in immer if that bothers you).

Example

import React from "react";
import Game from "sgame";
import { State, createInitialState, update, render } from "../ball";

const GamePage = () => (
  <Game<State>
    render={render}
    update={update}
    initialState={createInitialState()}
  />
);

Implementation of game in one file, ball.ts:

import {
  SCanvas,
  Point2D,
  Vector2D,
  v,
  Rect,
  Circle,
  clamp,
  RoundedRect
} from "solandra";
import { Update } from "sgame";

export type State = {
  time: number;
  ballPosition: Point2D;
  ballVelocity: Vector2D;
  paddlePosition: number;
  paddleDirection: -1 | 0 | 1;
  best: number;
  current: number;
};

export function createInitialState(): State {
  return {
    time: 0,
    ballPosition: [0.5, 0.5],
    ballVelocity: v.normalise([0.2, 0.5]),
    paddlePosition: 0.5,
    paddleDirection: 0,
    best: 0,
    current: 0
  };
}

export function update(state: State, update: Update) {
  switch (update.kind) {
    case "time":
      state.time += update.dT;
      state.ballPosition = v.add(
        v.scale(state.ballVelocity, update.dT),
        state.ballPosition
      );

      if (state.ballPosition[0] > 1) {
        state.ballVelocity[0] = -state.ballVelocity[0];
        state.ballPosition[0] = 1;
      }
      if (state.ballPosition[0] < 0) {
        state.ballVelocity[0] = -state.ballVelocity[0];
        state.ballPosition[0] = 0;
      }

      if (state.ballPosition[1] > 1) {
        if (Math.abs(state.ballPosition[0] - state.paddlePosition) < 0.075) {
          state.ballVelocity[1] = -state.ballVelocity[1];
          state.ballPosition[1] = 1;
          state.current++;
          if (state.current > state.best) state.best = state.current;
        } else {
          state.current = 0;
          state.ballPosition = [0.5, 0.5];
          state.ballVelocity = v.normalise([0.2, 0.5]);
        }
      }
      if (state.ballPosition[1] < 0) {
        state.ballVelocity[1] = -state.ballVelocity[1];
        state.ballPosition[1] = 0;
      }

      state.paddlePosition += state.paddleDirection * update.dT * 0.5;
      state.paddlePosition = clamp(
        { from: 0.1, to: 0.9 },
        state.paddlePosition
      );
      break;
    case "key":
      switch (update.key) {
        case "ArrowLeft":
          if (update.event === "down") {
            state.paddleDirection = -1;
          } else {
            state.paddleDirection = 0;
          }
          break;
        case "ArrowRight":
          if (update.event === "down") {
            state.paddleDirection = 1;
          } else {
            state.paddleDirection = 0;
          }
          break;
      }
  }
}

export function render(s: SCanvas, state: State) {
  const { bottom, center } = s.meta;
  const minD = Math.min(bottom, 1);
  const w = minD * 0.8;
  const h = minD * 0.8;
  const sX = (1 - w) / 2;
  const sY = (bottom - h) / 2;

  s.background(state.current * 5, 90, 20);

  s.setFillColor(state.current * 5, 80, 15);
  s.fill(
    new Rect({
      at: [sX, sY],
      w,
      h
    })
  );

  s.setFillColor(state.current * 5, 90, 30);
  s.fillText(
    {
      at: center,
      align: "center",
      size: 0.05
    },
    `${state.current} (Best: ${state.best})`
  );

  s.setFillColor(0, 0, 95);
  s.fill(
    new Circle({
      at: v.add([sX, sY], v.scale(state.ballPosition, w)),
      r: 0.02 * w
    })
  );

  s.fill(
    new RoundedRect({
      align: "center",
      at: [sX + w * state.paddlePosition, sY + h],
      w: 0.15 * w,
      h: 0.01 * w,
      r: 0.005
    })
  );
}