2048.cpp

# include <Siv3D.hpp>

constexpr int field_sz = 4;
constexpr int sz = 80;
constexpr int padding = 10;
constexpr int xBias = (800 - (sz * field_sz + padding * (field_sz - 1))) / 2;
constexpr int yBias = (600 - (sz * field_sz + padding * (field_sz - 1))) / 2;

struct Field2048 {
	int field[field_sz][field_sz];
	bool freeze[field_sz][field_sz];

	int prev_field[field_sz][field_sz];
	Array<std::pair<Point, Point>> prev_move;
	Array<Point> appear;

	Field2048() {
		for (int i = 0; i < field_sz; i++)
			for (int j = 0; j < field_sz; j++) {
				field[i][j] = -1;
				freeze[i][j] = false;
			}

		add_number(2);
		add_number(2);
	}

	Point add_number(int num) {
		Array<Point> blank;

		for (int i = 0; i < field_sz; i++)
			for (int j = 0; j < field_sz; j++) {
				if (field[i][j] == -1) {
					blank.push_back({ j, i });
				}
			}

		const auto &target = blank[Random(blank.size() - 1)];
		field[target.y][target.x] = num;

		return target;
	}

	void move_number(int x, int y, int dx, int dy) {
		if (field[y][x] == -1) return;
		auto px = x, py = y;

		while (0 <= x + dx && x + dx < field_sz && 0 <= y + dy && y + dy < field_sz) {
			if (field[y + dy][x + dx] == -1) {
				std::swap(field[y + dy][x + dx], field[y][x]);
			}
			else if (field[y + dy][x + dx] == field[y][x] && !freeze[y + dy][x + dx]) {
				field[y + dy][x + dx] += field[y][x];
				field[y][x] = -1;
				freeze[y + dy][x + dx] = true;
				y += dy;
				x += dx;
				break;
			}
			else {
				break;
			}
			y += dy;
			x += dx;
		}

		prev_move.push_back({ { px, py }, { x, y } });
	}

	bool operator!=(Field2048& other) const {
		for (int i = 0; i < field_sz; i++)
			for (int j = 0; j < field_sz; j++)
				if (field[i][j] != other.field[i][j]) return true;
		return false;
	}

	void apply(Field2048& after) {
		for (int i = 0; i < field_sz; i++)
			for (int j = 0; j < field_sz; j++) {
				prev_field[i][j] = field[i][j];
				field[i][j] = after.field[i][j];
				freeze[i][j] = false;
			}
		prev_move = after.prev_move;
		appear.clear();

		if (Random() <= 0.1) 
			appear.push_back(add_number(4));
		else 
			appear.push_back(add_number(2));
	}

	auto up() const {
		auto tmp = (*this);

		tmp.prev_move.clear();
		for (int i = 0; i < field_sz; i++)
			for (int j = 0; j < field_sz; j++) {
				tmp.move_number(i, j, -1, 0);
			}

		return tmp;
	}
	auto down() const {
		auto tmp = (*this);

		tmp.prev_move.clear();
		for (int i = field_sz - 1; i >= 0; i--)
			for (int j = 0; j < field_sz; j++) {
				tmp.move_number(i, j, +1, 0);
			}

		return tmp;
	}
	auto left() const {
		auto tmp = (*this);

		tmp.prev_move.clear();
		for (int i = 0; i < field_sz; i++)
			for (int j = 0; j < field_sz; j++) {
				tmp.move_number(j, i, 0, -1);
			}

		return tmp;
	}
	auto right() const {
		auto tmp = (*this);

		tmp.prev_move.clear();
		for (int i = field_sz - 1; i >= 0; i--)
			for (int j = 0; j < field_sz; j++) {
				tmp.move_number(j, i, 0, +1);
			}

		return tmp;
	}
};

void Main()
{
	const Font font{ 50 };
	bool gameover = false;

	Scene::SetBackground(ColorF{ 0.6, 0.8, 0.7 });

	Field2048 field;

	Timer animTimer;

	while (System::Update())
	{
		bool changed = false;
		if (!animTimer.isRunning()) {
			if (KeyUp.down()) {
				if (auto tmp = field.up(); field != tmp) {
					field.apply(tmp);
					changed = true;
				}
			}
			else if (KeyDown.down()) {
				if (auto tmp = field.down(); field != tmp) {
					field.apply(tmp);
					changed = true;
				}
			}
			else if (KeyLeft.down()) {
				if (auto tmp = field.left(); field != tmp) {
					field.apply(tmp);
					changed = true;
				}
			}
			else if (KeyRight.down()) {
				if (auto tmp = field.right(); field != tmp) {
					field.apply(tmp);
					changed = true;
				}
			}
		}

		if (changed) {
			animTimer.set(0.3s);
			animTimer.start();
			if (!(field.up() != field || field.down() != field || field.left() != field || field.right() != field)) {
				gameover = true;
			}
		}

		if (KeyR.down()) {
			field = Field2048{};
			gameover = false;
		}

		// Render
		Rect{ xBias - padding, yBias - padding, sz * field_sz + padding * (field_sz + 1), sz * field_sz + padding * (field_sz + 1)}.draw(Palette::White);
		for (int i = 0; i < field_sz; i++)
			for (int j = 0; j < field_sz; j++)
				Rect{ xBias + i * (sz + padding), yBias + j * (sz + padding), sz, sz }.draw(Palette::Lightgray);

		if (animTimer.isRunning()) {
			constexpr auto moveDur = 0.6;
			constexpr auto appearDur = 1 - moveDur;

			if (animTimer.progress0_1() / moveDur < 1.0) {
				for (const auto& [prev, cur] : field.prev_move) {
					auto p01 = EaseInOutCubic(Min(1.0, animTimer.progress0_1() / moveDur));
					auto p10 = 1 - p01;

					auto vx = xBias + (prev.y * p10 + cur.y * p01) * (sz + padding);
					auto vy = yBias + (prev.x * p10 + cur.x * p01) * (sz + padding);

					RectF{ vx, vy, sz, sz }.draw(Palette::Palegoldenrod);
					font(U"{}"_fmt(field.prev_field[prev.y][prev.x])).drawAt(vx + sz / 2, vy + sz / 2, Palette::Orange);
				}
			} else {
				for (const auto& [prev, cur] : field.prev_move) {
					auto vx = xBias + cur.y * (sz + padding);
					auto vy = yBias + cur.x * (sz + padding);

					RectF{ vx, vy, sz, sz }.draw(Palette::Palegoldenrod);
					font(U"{}"_fmt(field.field[cur.y][cur.x])).drawAt(vx + sz / 2, vy + sz / 2, Palette::Orange);
				}

				auto p01 = EaseOutSine((animTimer.progress0_1() - moveDur) / appearDur);

				for (const auto& pos : field.appear) {
					auto vx = xBias + pos.y * (sz + padding);
					auto vy = yBias + pos.x * (sz + padding);
					RectF{ vx, vy, sz, sz }.scaled(p01).draw(Palette::Palegoldenrod);
				}
			}
		}
		else {
			for (int i = 0; i < field_sz; i++)
				for (int j = 0; j < field_sz; j++)
				{
					if (field.field[i][j] != -1) {
						Rect{ xBias + i * (sz + padding), yBias + j * (sz + padding), sz, sz }.draw(Palette::Palegoldenrod);
						font(U"{}"_fmt(field.field[i][j])).drawAt(xBias + i * (sz + padding) + sz / 2, yBias + j * (sz + padding) + sz / 2, Palette::Orange);
					}
				}
		}

		if (gameover) {
			Rect{ 200, 200, 400, 200 }.draw(Palette::Gray);
			font(U"Game over").drawAt({ 400, 270 });
			font(U"R to restart").drawAt({ 400, 330 });
		}
	}
}