04マスなしで頭に距離制約で引かれる鎖状の胴体のヘビ
頭が餌へ向かって舵を取り、他の節は慣性で進みつつ隣の節との距離を一定に戻す制約を解くので、体が滑らかな曲線を描く。
使いどころ自由移動式のヘビ・虫キャラクター
SEG_GAPSTEER_RATESEG_COUNTFOLLOW_ITER
<main class="stage">
<div class="sc is-demo" id="scRoot">
<canvas class="sc__canvas" id="scCanvas" width="480" height="300" tabindex="0" aria-label="マスなしで頭に距離制約で引かれる鎖状の胴体のヘビ"></canvas>
<p class="sc__status" id="scStatus" aria-live="polite">自動操舵</p>
<button class="sc__btn" id="scBtn" type="button">一時停止</button>
<p class="sc__caption">マスなしで頭に距離制約で引かれる鎖状の胴体のヘビ</p>
</div>
</main>@use "../../../../site/static/demo-tokens" as *;
@include stage($stage-ink);
.sc {
position: relative;
width: min(92vw, calc(160vh - 12.8vw));
aspect-ratio: 480 / 300;
margin: 0 auto;
border-radius: $r-card;
overflow: hidden;
box-shadow: $shadow-raised;
background: $subject-ink;
}
.sc__canvas {
display: block;
width: 100%;
height: 100%;
touch-action: none;
}
.sc__canvas:focus-visible {
outline: 2px solid rgba(255, 255, 255, .85);
outline-offset: -6px;
}
.sc__status {
position: absolute;
left: $sp-3;
top: $sp-3;
max-width: 62%;
margin: 0;
padding: $sp-1 $sp-3;
border-radius: $r-pill;
background: rgba(255, 255, 255, .85);
color: $subject-ink;
font-weight: 500;
font-size: 11px;
line-height: 1.4;
pointer-events: none;
}
.sc__btn {
position: absolute;
right: $sp-3;
bottom: $sp-3;
margin: 0;
padding: $sp-1 $sp-3;
border: 0;
border-radius: $r-pill;
background: rgba(255, 255, 255, .85);
color: $subject-ink;
font: inherit;
font-weight: 500;
font-size: 12px;
line-height: 1.4;
cursor: pointer;
}
.sc__btn:focus-visible {
outline: 2px solid #ffffff;
outline-offset: 2px;
}
.sc__caption {
position: absolute;
left: $sp-3;
bottom: $sp-3;
max-width: 68%;
margin: 0;
padding: $sp-1 $sp-3;
border-radius: $r-pill;
background: rgba(255, 255, 255, .85);
color: $subject-ink;
font-weight: 500;
font-size: 12px;
line-height: 1.4;
pointer-events: none;
}
@media (max-width: 340px) {
.sc__caption, .sc__btn { font-size: 10px; padding: $sp-1 $sp-2; }
.sc__status { font-size: 10px; }
}
@media (prefers-reduced-motion: reduce) {
.sc { cursor: default; }
}html, body {
margin: 0;
overflow: hidden;
}
.stage {
box-sizing: border-box;
min-height: 100vh;
display: grid;
place-items: center;
margin: 0;
background: #17141a;
font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
padding: clamp(8px, 4vw, 24px);
}
.sc {
position: relative;
width: min(92vw, 160vh - 12.8vw);
aspect-ratio: 480/300;
margin: 0 auto;
border-radius: 16px;
overflow: hidden;
box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
background: #17141a;
}
.sc__canvas {
display: block;
width: 100%;
height: 100%;
touch-action: none;
}
.sc__canvas:focus-visible {
outline: 2px solid rgba(255, 255, 255, 0.85);
outline-offset: -6px;
}
.sc__status {
position: absolute;
left: 12px;
top: 12px;
max-width: 62%;
margin: 0;
padding: 4px 12px;
border-radius: 999px;
background: rgba(255, 255, 255, 0.85);
color: #17141a;
font-weight: 500;
font-size: 11px;
line-height: 1.4;
pointer-events: none;
}
.sc__btn {
position: absolute;
right: 12px;
bottom: 12px;
margin: 0;
padding: 4px 12px;
border: 0;
border-radius: 999px;
background: rgba(255, 255, 255, 0.85);
color: #17141a;
font: inherit;
font-weight: 500;
font-size: 12px;
line-height: 1.4;
cursor: pointer;
}
.sc__btn:focus-visible {
outline: 2px solid #ffffff;
outline-offset: 2px;
}
.sc__caption {
position: absolute;
left: 12px;
bottom: 12px;
max-width: 68%;
margin: 0;
padding: 4px 12px;
border-radius: 999px;
background: rgba(255, 255, 255, 0.85);
color: #17141a;
font-weight: 500;
font-size: 12px;
line-height: 1.4;
pointer-events: none;
}
@media (max-width: 340px) {
.sc__caption, .sc__btn {
font-size: 10px;
padding: 4px 8px;
}
.sc__status {
font-size: 10px;
}
}
@media (prefers-reduced-motion: reduce) {
.sc {
cursor: default;
}
}(function () {
const W = 480;
const H = 300;
const PI2 = Math.PI * 2;
const FIXED_DT = 16;
const REDUCE_STEP_MS = 900;
const IDLE_TICKS = 150;
const BTN_PAUSE = '一時停止';
const BTN_PLAY = '再生';
const BTN_NEXT = '次の場面';
// 파스텔 팔레트 — 어두운 판 위에 밝은 색을 얹어 명도 차로 읽힌다
const BG = [29, 26, 44];
const TILE_A = [37, 33, 58];
const TILE_B = [42, 38, 66];
const MINT = [126, 226, 192];
const SKY = [124, 196, 255];
const LILAC = [190, 164, 255];
const PINK = [255, 160, 190];
const PEACH = [255, 208, 168];
const CREAM = [255, 244, 224];
function clamp(v, lo, hi) { return v < lo ? lo : (v > hi ? hi : v); }
function lerp(a, b, k) { return a + (b - a) * k; }
function smooth(x) { const c = clamp(x, 0, 1); return c * c * (3 - 2 * c); }
function rgba(c, a) {
return 'rgba(' + Math.round(c[0]) + ',' + Math.round(c[1]) + ',' + Math.round(c[2]) + ',' + clamp(a, 0, 1).toFixed(3) + ')';
}
function mix(a, b, k) {
return [lerp(a[0], b[0], k), lerp(a[1], b[1], k), lerp(a[2], b[2], k)];
}
// 시드 고정 난수 — 같은 시드면 언제나 같은 수열 (선형 합동 방식)
function lcg(seed) {
let s = seed >>> 0;
return function () {
s = (Math.imul(s, 1664525) + 1013904223) >>> 0;
return s / 4294967296;
};
}
// 정수 두 개로 0 이상 1 미만의 값을 만드는 해시 (같은 입력은 늘 같은 값)
function hash2(x, y, seed) {
let h = (Math.imul(x | 0, 374761393) + Math.imul(y | 0, 668265263) + Math.imul(seed | 0, 1442695041)) | 0;
h = Math.imul(h ^ (h >>> 13), 1274126177);
h ^= h >>> 16;
return (h >>> 0) / 4294967296;
}
function glow(ctx, x, y, r, c, a) {
const g = ctx.createRadialGradient(x, y, 0, x, y, r);
g.addColorStop(0, rgba(c, a));
g.addColorStop(1, rgba(c, 0));
ctx.fillStyle = g;
ctx.fillRect(x - r, y - r, r * 2, r * 2);
}
// 둥근 사각형 경로 (roundRect 가 없는 브라우저에서도 같은 모양)
function rrPath(ctx, x, y, w, h, r) {
const rr = Math.min(r, w / 2, h / 2);
ctx.beginPath();
ctx.moveTo(x + rr, y);
ctx.arcTo(x + w, y, x + w, y + h, rr);
ctx.arcTo(x + w, y + h, x, y + h, rr);
ctx.arcTo(x, y + h, x, y, rr);
ctx.arcTo(x, y, x + w, y, rr);
ctx.closePath();
}
function makeBoard(rows) {
const cell = H / rows;
const cols = Math.floor(W / cell + 1e-6);
return { cols: cols, rows: rows, cell: cell, ox: (W - cols * cell) / 2, oy: 0, n: cols * rows };
}
const DX = [0, 1, 0, -1];
const DY = [-1, 0, 1, 0];
// 칸 번호 y*cols+x. 판 밖이면 -1 (wrap 이면 반대편으로 이어진다)
function cellAt(b, x, y, wrap) {
let xx = x;
let yy = y;
if (wrap) {
xx = (x % b.cols + b.cols) % b.cols;
yy = (y % b.rows + b.rows) % b.rows;
}
else if (x < 0 || y < 0 || x >= b.cols || y >= b.rows) {
return -1;
}
return yy * b.cols + xx;
}
function neighborCell(b, i, d, wrap) {
return cellAt(b, (i % b.cols) + DX[d], Math.floor(i / b.cols) + DY[d], wrap);
}
// 목표 칸에서 너비 우선으로 퍼지는 거리장. blocked 칸과 닿지 못하는 칸은 -1
function distField(b, target, blocked, wrap) {
const dist = new Int16Array(b.n).fill(-1);
const queue = new Int16Array(b.n);
let qh = 0;
let qt = 0;
dist[target] = 0;
queue[qt] = target;
qt += 1;
while (qh < qt) {
const c = queue[qh];
qh += 1;
for (let d = 0; d < 4; d += 1) {
const nb = neighborCell(b, c, d, wrap);
if (nb >= 0 && dist[nb] < 0 && blocked[nb] === 0) {
dist[nb] = dist[c] + 1;
queue[qt] = nb;
qt += 1;
}
}
}
return dist;
}
// 거리장에서 값이 가장 낮은 이웃 (없으면 -1)
function lowestNeighbor(b, dist, from, wrap) {
let best = -1;
let bv = 32000;
for (let d = 0; d < 4; d += 1) {
const nb = neighborCell(b, from, d, wrap);
if (nb >= 0 && dist[nb] >= 0 && dist[nb] < bv) {
bv = dist[nb];
best = nb;
}
}
return best;
}
function pathFrom(b, dist, head, wrap) {
const path = [];
let cur = head;
for (let k = 0; k < b.n; k += 1) {
const nx = lowestNeighbor(b, dist, cur, wrap);
if (nx < 0 || (dist[nx] >= dist[cur] && cur !== head)) {
return [];
}
path.push(nx);
if (dist[nx] === 0) {
return path;
}
cur = nx;
}
return [];
}
function placeFood(g) {
const used = new Uint8Array(g.b.n);
for (let i = 0; i < g.body.length; i += 1) {
used[g.body[i]] = 1;
}
const free = [];
for (let i = 0; i < g.b.n; i += 1) {
if (used[i] === 0) {
free.push(i);
}
}
g.food = free.length > 0 ? free[Math.floor(g.rnd() * free.length)] : -1;
}
function resetGame(g) {
const b = g.b;
const hx = Math.floor(b.cols / 2);
const hy = Math.floor(b.rows / 2);
g.body = [hy * b.cols + hx, hy * b.cols + hx - 1, hy * b.cols + hx - 2];
g.prev = g.body.slice();
g.dead = false;
g.resets += 1;
placeFood(g);
}
function newGame(b, wrap, seed) {
const g = { b: b, wrap: wrap, body: [], prev: [], food: -1, rnd: lcg(seed), eaten: 0, dead: false, resets: -1 };
resetGame(g);
return g;
}
// 머리를 next 칸으로 옮긴다. 먹으면 true, 몸에 부딪히면 dead
function moveSnake(g, next) {
g.prev = g.body.slice();
const ate = next === g.food;
const tail = g.body[g.body.length - 1];
for (let i = 0; i < g.body.length; i += 1) {
if (g.body[i] === next && !(i === g.body.length - 1 && !ate && next === tail)) {
g.dead = true;
return false;
}
}
g.body.unshift(next);
if (ate) {
g.eaten += 1;
placeFood(g);
}
else {
g.body.pop();
}
return ate;
}
// 경로를 끝까지 따라가 먹은 뒤의 가상 몸
function simulate(body, path) {
const v = body.slice();
for (let k = 0; k < path.length; k += 1) {
v.unshift(path[k]);
if (k < path.length - 1) {
v.pop();
}
}
return v;
}
// 가상 몸의 머리에서 번져 나가 꼬리에 닿는가. mark 를 주면 닿은 칸을 표시한다
function tailReachable(b, v, wrap, mark) {
const blocked = new Uint8Array(b.n);
for (let i = 1; i < v.length - 1; i += 1) {
blocked[v[i]] = 1;
}
const tail = v[v.length - 1];
const head = v[0];
const seen = new Uint8Array(b.n);
const stack = [head];
seen[head] = 1;
let hit = false;
while (stack.length > 0) {
const c = stack.pop();
for (let d = 0; d < 4; d += 1) {
const nb = neighborCell(b, c, d, wrap);
if (nb < 0 || seen[nb] === 1) {
continue;
}
if (nb === tail) {
hit = true;
continue;
}
if (blocked[nb] === 1 || nb === head) {
continue;
}
seen[nb] = 1;
stack.push(nb);
}
}
if (mark) {
mark.set(seen);
}
return hit;
}
// 한 수를 정한다: 먹이까지 최단 경로 → (안전 검사) → 막히면 꼬리를 쫓는다
function planMove(g, safeOn) {
const b = g.b;
const head = g.body[0];
const tail = g.body[g.body.length - 1];
const plan = { next: -1, path: [], rejected: [], trap: new Uint8Array(b.n), chase: false };
const blocked = new Uint8Array(b.n);
for (let i = 0; i < g.body.length - 1; i += 1) {
blocked[g.body[i]] = 1;
}
if (g.food >= 0) {
const dist = distField(b, g.food, blocked, g.wrap);
const path = pathFrom(b, dist, head, g.wrap);
plan.path = path;
if (path.length > 0) {
if (!safeOn) {
plan.next = path[0];
return plan;
}
const v = simulate(g.body, path);
if (tailReachable(b, v, g.wrap, plan.trap)) {
plan.next = path[0];
return plan;
}
plan.rejected = path;
}
}
plan.chase = true;
const dist2 = distField(b, tail, blocked, g.wrap);
const nx = lowestNeighbor(b, dist2, head, g.wrap);
if (nx >= 0) {
plan.next = nx;
return plan;
}
for (let d = 0; d < 4; d += 1) {
const nb = neighborCell(b, head, d, g.wrap);
if (nb >= 0 && blocked[nb] === 0 && nb !== head) {
plan.next = nb;
return plan;
}
}
return plan;
}
// 칸 중심의 화면 좌표
function cellX(b, i) { return b.ox + ((i % b.cols) + 0.5) * b.cell; }
function cellY(b, i) { return b.oy + (Math.floor(i / b.cols) + 0.5) * b.cell; }
function wrapDelta(a, c, n, wrap) {
let d = c - a;
if (wrap) {
if (d > n / 2) {
d -= n;
}
if (d < -n / 2) {
d += n;
}
}
return d;
}
// 節 i 의 보간 위치 (칸 좌표). 지난 틱의 자리에서 이번 틱의 자리로 p(0~1) 만큼
function segPos(g, i, p) {
const b = g.b;
const cur = g.body[i];
const pv = i < g.prev.length ? g.prev[i] : cur;
const cx = cur % b.cols;
const cy = Math.floor(cur / b.cols);
const px = pv % b.cols;
const py = Math.floor(pv / b.cols);
return [px + wrapDelta(px, cx, b.cols, g.wrap) * p, py + wrapDelta(py, cy, b.rows, g.wrap) * p];
}
function drawTiles(ctx, b) {
ctx.fillStyle = rgba(BG, 1);
ctx.fillRect(0, 0, W, H);
for (let y = 0; y < b.rows; y += 1) {
for (let x = 0; x < b.cols; x += 1) {
ctx.fillStyle = rgba((x + y) % 2 === 0 ? TILE_A : TILE_B, 1);
ctx.fillRect(b.ox + x * b.cell, b.oy + y * b.cell, b.cell + 0.5, b.cell + 0.5);
}
}
}
function drawFood(ctx, b, food, t) {
if (food < 0) {
return;
}
const x = cellX(b, food);
const y = cellY(b, food);
const pulse = 0.5 + 0.5 * Math.sin(t * 0.12);
glow(ctx, x, y, b.cell * (1.3 + 0.35 * pulse), PINK, 0.55);
ctx.fillStyle = rgba(PINK, 1);
ctx.beginPath();
ctx.arc(x, y, b.cell * 0.3, 0, PI2);
ctx.fill();
ctx.fillStyle = rgba(CREAM, 0.9);
ctx.beginPath();
ctx.arc(x - b.cell * 0.08, y - b.cell * 0.09, b.cell * 0.09, 0, PI2);
ctx.fill();
}
function bodyColor(i, len) {
return mix(MINT, SKY, len <= 1 ? 0 : i / (len - 1));
}
// 칸 중심 (x,y 칸 좌표, 소수 허용)에 節 하나
function drawSeg(ctx, b, gx, gy, c, shrink) {
const s = b.cell * (1 - shrink);
const cx = b.ox + (gx + 0.5) * b.cell;
const cy = b.oy + (gy + 0.5) * b.cell;
ctx.fillStyle = rgba(c, 1);
rrPath(ctx, cx - s / 2, cy - s / 2, s, s, s * 0.32);
ctx.fill();
}
function drawEyes(ctx, b, gx, gy, dirx, diry) {
const cx = b.ox + (gx + 0.5) * b.cell;
const cy = b.oy + (gy + 0.5) * b.cell;
const px = -diry;
const py = dirx;
const r = b.cell * 0.09;
ctx.fillStyle = rgba(BG, 1);
for (let s = -1; s <= 1; s += 2) {
ctx.beginPath();
ctx.arc(cx + dirx * b.cell * 0.16 + px * s * b.cell * 0.18, cy + diry * b.cell * 0.16 + py * s * b.cell * 0.18, r, 0, PI2);
ctx.fill();
}
}
function headDir(g) {
if (g.body.length < 2) {
return [1, 0];
}
const b = g.b;
const dx = wrapDelta(g.body[1] % b.cols, g.body[0] % b.cols, b.cols, g.wrap);
const dy = wrapDelta(Math.floor(g.body[1] / b.cols), Math.floor(g.body[0] / b.cols), b.rows, g.wrap);
return [clamp(dx, -1, 1), clamp(dy, -1, 1)];
}
// 보간 없이 칸 그대로 그리는 기본 뱀
function drawSnakeCells(ctx, g, dim) {
const len = g.body.length;
for (let i = len - 1; i >= 0; i -= 1) {
const c = g.body[i];
const col = mix(bodyColor(i, len), BG, dim);
drawSeg(ctx, g.b, c % g.b.cols, Math.floor(c / g.b.cols), col, 0.08);
}
const hd = headDir(g);
drawEyes(ctx, g.b, g.body[0] % g.b.cols, Math.floor(g.body[0] / g.b.cols), hd[0], hd[1]);
}
function start(root, canvas, statusEl, btnEl, make) {
const ctx0 = canvas.getContext('2d');
if (!ctx0) {
return function () { return; };
}
const ctx = ctx0;
const dpr = Math.min(window.devicePixelRatio || 1, 2);
canvas.width = Math.round(W * dpr);
canvas.height = Math.round(H * dpr);
ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
const reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
const inp = { x: W / 2, y: H / 2, idle: 99999 };
const scene = make(inp, reduce);
let paused = false;
let rafId = 0;
let lastTs = -1;
let accMs = 0;
let lastLabel = '';
const cleaners = [];
function listen(target, type, fn) {
target.addEventListener(type, fn);
cleaners.push(function () { target.removeEventListener(type, fn); });
}
function show() {
scene.draw(ctx);
const t = scene.label();
if (t !== lastLabel) {
lastLabel = t;
statusEl.textContent = t;
}
}
function advance(ms) {
const n = Math.round(ms / FIXED_DT);
for (let i = 0; i < n; i += 1) {
inp.idle += 1;
scene.step();
}
}
// 움직임 줄이기에서는 루프가 없으니 입력 직후 한 틱쯤 앞으로 보내 바로 그린다
function refresh() {
if (reduce) {
advance(FIXED_DT * 8);
show();
}
}
function toLocal(e) {
const r = canvas.getBoundingClientRect();
inp.x = clamp((e.clientX - r.left) * W / r.width, 0, W);
inp.y = clamp((e.clientY - r.top) * H / r.height, 0, H);
inp.idle = 0;
}
function tick(ts) {
if (lastTs < 0) {
lastTs = ts;
}
const frameDt = Math.min(ts - lastTs, 160);
lastTs = ts;
if (!paused) {
accMs += frameDt;
while (accMs >= FIXED_DT) {
inp.idle += 1;
scene.step();
accMs -= FIXED_DT;
}
show();
}
rafId = requestAnimationFrame(tick);
}
btnEl.textContent = reduce ? BTN_NEXT : BTN_PAUSE;
if (reduce) {
root.classList.remove('is-demo');
advance(1400);
show();
}
listen(btnEl, 'click', function () {
if (reduce) {
advance(REDUCE_STEP_MS);
show();
return;
}
paused = !paused;
if (paused) {
root.classList.remove('is-demo');
}
else {
root.classList.add('is-demo');
}
btnEl.textContent = paused ? BTN_PLAY : BTN_PAUSE;
});
listen(canvas, 'pointermove', function (e) {
toLocal(e);
refresh();
});
listen(canvas, 'pointerdown', function (e) {
toLocal(e);
scene.tap();
refresh();
});
listen(canvas, 'keydown', function (e) {
const k = e.key;
if (k === 'Enter' || k === ' ') {
e.preventDefault();
scene.tap();
refresh();
return;
}
// 이 장면이 쓰는 키만 막는다. 쓰지 않는 키(Tab 등)는 그대로 둔다
if (scene.key(k)) {
e.preventDefault();
refresh();
}
});
if (!reduce) {
rafId = requestAnimationFrame(tick);
}
return function () {
cancelAnimationFrame(rafId);
for (let i = 0; i < cleaners.length; i += 1) {
cleaners[i]();
}
};
}
const SEG_GAP = 9;
const SEG_COUNT = 26;
const SEG_MAX = 40;
const STEER_RATE = 0.075;
const FOLLOW_ITER = 4;
const FOLLOW_STIFF = 0.85;
const SPEED = 2.3;
const DAMP = 0.97;
const EAT_R = 11;
const WALL_PAD = 34;
const KEY_HOLD = 36;
const TRAIL_KEEP = 0.34;
const TXT_AUTO = '自動操舵';
const TXT_POINTER = 'ポインターを追跡中';
const TXT_KEYS = '矢印キー操作';
const TXT_LEN = '節';
const TXT_SCORE = '食べた数';
function makeScene(inp, reduce) {
const rnd = lcg(455404);
const px = [];
const py = [];
const qx = [];
const qy = [];
let ang = 0.3;
let fx = 0;
let fy = 0;
let t = 0;
let eaten = 0;
let keyAng = 0;
let keyLeft = 0;
let count = SEG_COUNT;
let painted = false;
function placeFoodAt() {
fx = 40 + rnd() * (W - 80);
fy = 36 + rnd() * (H - 72);
}
placeFoodAt();
for (let i = 0; i < SEG_MAX; i += 1) {
px.push(W * 0.3 - i * SEG_GAP);
py.push(H * 0.55);
qx.push(px[i]);
qy.push(py[i]);
}
function angDiff(a, c) {
let d = c - a;
while (d > Math.PI) {
d -= PI2;
}
while (d < -Math.PI) {
d += PI2;
}
return d;
}
const scene = {
step() {
t += 1;
let goalX = fx;
let goalY = fy;
if (inp.idle < IDLE_TICKS) {
goalX = inp.x;
goalY = inp.y;
}
let want = Math.atan2(goalY - py[0], goalX - px[0]);
if (keyLeft > 0) {
keyLeft -= 1;
want = keyAng;
}
// 벽 가까이에서는 판 가운데 쪽으로 틀어 준다
if (px[0] < WALL_PAD || px[0] > W - WALL_PAD || py[0] < WALL_PAD || py[0] > H - WALL_PAD) {
want = Math.atan2(H / 2 - py[0], W / 2 - px[0]);
}
ang += clamp(angDiff(ang, want), -STEER_RATE, STEER_RATE) + Math.sin(t * 0.11) * 0.018;
// 머리만 직접 움직이고 나머지 마디는 이전 위치와의 차이(관성)로 나아간다
qx[0] = px[0];
qy[0] = py[0];
px[0] += Math.cos(ang) * SPEED;
py[0] += Math.sin(ang) * SPEED;
for (let i = 1; i < count; i += 1) {
const vx = (px[i] - qx[i]) * DAMP;
const vy = (py[i] - qy[i]) * DAMP;
qx[i] = px[i];
qy[i] = py[i];
px[i] += vx;
py[i] += vy;
}
// 거리 제약: 이웃 마디와의 간격을 SEG_GAP 으로 되돌린다
for (let it = 0; it < FOLLOW_ITER; it += 1) {
for (let i = 1; i < count; i += 1) {
const dx = px[i] - px[i - 1];
const dy = py[i] - py[i - 1];
const d = Math.sqrt(dx * dx + dy * dy) || 0.0001;
const k = ((d - SEG_GAP) / d) * FOLLOW_STIFF;
if (i === 1) {
px[i] -= dx * k;
py[i] -= dy * k;
}
else {
px[i] -= dx * k * 0.5;
py[i] -= dy * k * 0.5;
px[i - 1] += dx * k * 0.5;
py[i - 1] += dy * k * 0.5;
}
}
}
const ex = px[0] - fx;
const ey = py[0] - fy;
if (ex * ex + ey * ey < EAT_R * EAT_R) {
eaten += 1;
if (count < SEG_MAX) {
count += 1;
px[count - 1] = px[count - 2];
py[count - 1] = py[count - 2];
qx[count - 1] = px[count - 1];
qy[count - 1] = py[count - 1];
}
placeFoodAt();
}
},
draw(ctx) {
// 배경을 반투명으로 덮어 지난 자리가 몇 프레임 남게 한다 (첫 프레임만 불투명)
ctx.fillStyle = rgba(BG, painted ? TRAIL_KEEP : 1);
ctx.fillRect(0, 0, W, H);
painted = true;
// 바닥 격자 — 칸 없는 판이라는 걸 보여 주려고 아주 옅게
ctx.strokeStyle = rgba(LILAC, 0.1);
ctx.lineWidth = 1;
for (let x = 0; x <= W; x += 30) {
ctx.beginPath();
ctx.moveTo(x, 0);
ctx.lineTo(x, H);
ctx.stroke();
}
for (let y = 0; y <= H; y += 30) {
ctx.beginPath();
ctx.moveTo(0, y);
ctx.lineTo(W, y);
ctx.stroke();
}
const pulse = 0.5 + 0.5 * Math.sin(t * 0.12);
glow(ctx, fx, fy, 22 + 6 * pulse, PINK, 0.6);
ctx.fillStyle = rgba(PINK, 1);
ctx.beginPath();
ctx.arc(fx, fy, 6.5, 0, PI2);
ctx.fill();
// 지난 자리 잔상 — 이전 위치(qx,qy)에서 지금 위치로 끄는 꼬리빛
for (let i = count - 1; i >= 0; i -= 1) {
const f = i / count;
const c = mix(MINT, SKY, f);
glow(ctx, qx[i], qy[i], 13 - 5 * f, c, 0.22);
}
for (let i = count - 1; i >= 0; i -= 1) {
const f = i / count;
const r = 6.4 - 3.4 * f;
ctx.fillStyle = rgba(mix(MINT, SKY, f), 1);
ctx.beginPath();
ctx.arc(px[i], py[i], r, 0, PI2);
ctx.fill();
}
ctx.fillStyle = rgba(BG, 1);
for (let s = -1; s <= 1; s += 2) {
ctx.beginPath();
ctx.arc(px[0] + Math.cos(ang) * 2.4 - Math.sin(ang) * s * 2.8, py[0] + Math.sin(ang) * 2.4 + Math.cos(ang) * s * 2.8, 1.3, 0, PI2);
ctx.fill();
}
},
label() {
const mode = keyLeft > 0 ? TXT_KEYS : (inp.idle < IDLE_TICKS ? TXT_POINTER : TXT_AUTO);
return mode + ' · ' + TXT_LEN + ' ' + count + ' · ' + TXT_SCORE + ' ' + eaten;
},
tap() {
placeFoodAt();
},
key(k) {
if (k === 'ArrowLeft') {
keyAng = Math.PI;
}
else if (k === 'ArrowRight') {
keyAng = 0;
}
else if (k === 'ArrowUp') {
keyAng = -Math.PI / 2;
}
else if (k === 'ArrowDown') {
keyAng = Math.PI / 2;
}
else {
return false;
}
keyLeft = KEY_HOLD;
return true;
}
};
if (reduce) {
for (let i = 0; i < 60; i += 1) {
scene.step();
}
}
return scene;
}
start(document.getElementById('scRoot'), document.getElementById('scCanvas'), document.getElementById('scStatus'), document.getElementById('scBtn'), makeScene);
})();import { useEffect, useRef } from "react";
import styles from "./SkChainFollowRope.module.scss";
const W = 480;
const H = 300;
const PI2 = Math.PI * 2;
const FIXED_DT = 16;
const REDUCE_STEP_MS = 900;
const IDLE_TICKS = 150;
const BTN_PAUSE = '멈춤';
const BTN_PLAY = '재생';
const BTN_NEXT = '다음 장면';
type RGB = [number, number, number];
interface Input { x: number; y: number; idle: number; }
interface Scene {
step(): void;
draw(ctx: CanvasRenderingContext2D): void;
label(): string;
tap(): void;
key(k: string): boolean;
}
type Maker = (inp: Input, reduce: boolean) => Scene;
// 파스텔 팔레트 — 어두운 판 위에 밝은 색을 얹어 명도 차로 읽힌다
const BG: RGB = [29, 26, 44];
const TILE_A: RGB = [37, 33, 58];
const TILE_B: RGB = [42, 38, 66];
const MINT: RGB = [126, 226, 192];
const SKY: RGB = [124, 196, 255];
const LILAC: RGB = [190, 164, 255];
const PINK: RGB = [255, 160, 190];
const PEACH: RGB = [255, 208, 168];
const CREAM: RGB = [255, 244, 224];
function clamp(v: number, lo: number, hi: number): number { return v < lo ? lo : (v > hi ? hi : v); }
function lerp(a: number, b: number, k: number): number { return a + (b - a) * k; }
function smooth(x: number): number { const c = clamp(x, 0, 1); return c * c * (3 - 2 * c); }
function rgba(c: RGB, a: number): string {
return 'rgba(' + Math.round(c[0]) + ',' + Math.round(c[1]) + ',' + Math.round(c[2]) + ',' + clamp(a, 0, 1).toFixed(3) + ')';
}
function mix(a: RGB, b: RGB, k: number): RGB {
return [lerp(a[0], b[0], k), lerp(a[1], b[1], k), lerp(a[2], b[2], k)];
}
// 시드 고정 난수 — 같은 시드면 언제나 같은 수열 (선형 합동 방식)
function lcg(seed: number): () => number {
let s = seed >>> 0;
return function (): number {
s = (Math.imul(s, 1664525) + 1013904223) >>> 0;
return s / 4294967296;
};
}
// 정수 두 개로 0 이상 1 미만의 값을 만드는 해시 (같은 입력은 늘 같은 값)
function hash2(x: number, y: number, seed: number): number {
let h = (Math.imul(x | 0, 374761393) + Math.imul(y | 0, 668265263) + Math.imul(seed | 0, 1442695041)) | 0;
h = Math.imul(h ^ (h >>> 13), 1274126177);
h ^= h >>> 16;
return (h >>> 0) / 4294967296;
}
function glow(ctx: CanvasRenderingContext2D, x: number, y: number, r: number, c: RGB, a: number): void {
const g = ctx.createRadialGradient(x, y, 0, x, y, r);
g.addColorStop(0, rgba(c, a));
g.addColorStop(1, rgba(c, 0));
ctx.fillStyle = g;
ctx.fillRect(x - r, y - r, r * 2, r * 2);
}
// 둥근 사각형 경로 (roundRect 가 없는 브라우저에서도 같은 모양)
function rrPath(ctx: CanvasRenderingContext2D, x: number, y: number, w: number, h: number, r: number): void {
const rr = Math.min(r, w / 2, h / 2);
ctx.beginPath();
ctx.moveTo(x + rr, y);
ctx.arcTo(x + w, y, x + w, y + h, rr);
ctx.arcTo(x + w, y + h, x, y + h, rr);
ctx.arcTo(x, y + h, x, y, rr);
ctx.arcTo(x, y, x + w, y, rr);
ctx.closePath();
}
// ---- 판과 뱀 ----
interface Board { cols: number; rows: number; cell: number; ox: number; oy: number; n: number; }
function makeBoard(rows: number): Board {
const cell = H / rows;
const cols = Math.floor(W / cell + 1e-6);
return { cols: cols, rows: rows, cell: cell, ox: (W - cols * cell) / 2, oy: 0, n: cols * rows };
}
const DX = [0, 1, 0, -1];
const DY = [-1, 0, 1, 0];
// 칸 번호 y*cols+x. 판 밖이면 -1 (wrap 이면 반대편으로 이어진다)
function cellAt(b: Board, x: number, y: number, wrap: boolean): number {
let xx = x;
let yy = y;
if (wrap) {
xx = (x % b.cols + b.cols) % b.cols;
yy = (y % b.rows + b.rows) % b.rows;
} else if (x < 0 || y < 0 || x >= b.cols || y >= b.rows) {
return -1;
}
return yy * b.cols + xx;
}
function neighborCell(b: Board, i: number, d: number, wrap: boolean): number {
return cellAt(b, (i % b.cols) + DX[d], Math.floor(i / b.cols) + DY[d], wrap);
}
// 목표 칸에서 너비 우선으로 퍼지는 거리장. blocked 칸과 닿지 못하는 칸은 -1
function distField(b: Board, target: number, blocked: Uint8Array, wrap: boolean): Int16Array {
const dist = new Int16Array(b.n).fill(-1);
const queue = new Int16Array(b.n);
let qh = 0;
let qt = 0;
dist[target] = 0;
queue[qt] = target;
qt += 1;
while (qh < qt) {
const c = queue[qh];
qh += 1;
for (let d = 0; d < 4; d += 1) {
const nb = neighborCell(b, c, d, wrap);
if (nb >= 0 && dist[nb] < 0 && blocked[nb] === 0) {
dist[nb] = dist[c] + 1;
queue[qt] = nb;
qt += 1;
}
}
}
return dist;
}
// 거리장에서 값이 가장 낮은 이웃 (없으면 -1)
function lowestNeighbor(b: Board, dist: Int16Array, from: number, wrap: boolean): number {
let best = -1;
let bv = 32000;
for (let d = 0; d < 4; d += 1) {
const nb = neighborCell(b, from, d, wrap);
if (nb >= 0 && dist[nb] >= 0 && dist[nb] < bv) {
bv = dist[nb];
best = nb;
}
}
return best;
}
function pathFrom(b: Board, dist: Int16Array, head: number, wrap: boolean): number[] {
const path: number[] = [];
let cur = head;
for (let k = 0; k < b.n; k += 1) {
const nx = lowestNeighbor(b, dist, cur, wrap);
if (nx < 0 || (dist[nx] >= dist[cur] && cur !== head)) {
return [];
}
path.push(nx);
if (dist[nx] === 0) {
return path;
}
cur = nx;
}
return [];
}
interface Game {
b: Board;
wrap: boolean;
body: number[];
prev: number[];
food: number;
rnd: () => number;
eaten: number;
dead: boolean;
resets: number;
}
function placeFood(g: Game): void {
const used = new Uint8Array(g.b.n);
for (let i = 0; i < g.body.length; i += 1) {
used[g.body[i]] = 1;
}
const free: number[] = [];
for (let i = 0; i < g.b.n; i += 1) {
if (used[i] === 0) {
free.push(i);
}
}
g.food = free.length > 0 ? free[Math.floor(g.rnd() * free.length)] : -1;
}
function resetGame(g: Game): void {
const b = g.b;
const hx = Math.floor(b.cols / 2);
const hy = Math.floor(b.rows / 2);
g.body = [hy * b.cols + hx, hy * b.cols + hx - 1, hy * b.cols + hx - 2];
g.prev = g.body.slice();
g.dead = false;
g.resets += 1;
placeFood(g);
}
function newGame(b: Board, wrap: boolean, seed: number): Game {
const g: Game = { b: b, wrap: wrap, body: [], prev: [], food: -1, rnd: lcg(seed), eaten: 0, dead: false, resets: -1 };
resetGame(g);
return g;
}
// 머리를 next 칸으로 옮긴다. 먹으면 true, 몸에 부딪히면 dead
function moveSnake(g: Game, next: number): boolean {
g.prev = g.body.slice();
const ate = next === g.food;
const tail = g.body[g.body.length - 1];
for (let i = 0; i < g.body.length; i += 1) {
if (g.body[i] === next && !(i === g.body.length - 1 && !ate && next === tail)) {
g.dead = true;
return false;
}
}
g.body.unshift(next);
if (ate) {
g.eaten += 1;
placeFood(g);
} else {
g.body.pop();
}
return ate;
}
// 경로를 끝까지 따라가 먹은 뒤의 가상 몸
function simulate(body: number[], path: number[]): number[] {
const v = body.slice();
for (let k = 0; k < path.length; k += 1) {
v.unshift(path[k]);
if (k < path.length - 1) {
v.pop();
}
}
return v;
}
// 가상 몸의 머리에서 번져 나가 꼬리에 닿는가. mark 를 주면 닿은 칸을 표시한다
function tailReachable(b: Board, v: number[], wrap: boolean, mark: Uint8Array | null): boolean {
const blocked = new Uint8Array(b.n);
for (let i = 1; i < v.length - 1; i += 1) {
blocked[v[i]] = 1;
}
const tail = v[v.length - 1];
const head = v[0];
const seen = new Uint8Array(b.n);
const stack: number[] = [head];
seen[head] = 1;
let hit = false;
while (stack.length > 0) {
const c = stack.pop() as number;
for (let d = 0; d < 4; d += 1) {
const nb = neighborCell(b, c, d, wrap);
if (nb < 0 || seen[nb] === 1) {
continue;
}
if (nb === tail) {
hit = true;
continue;
}
if (blocked[nb] === 1 || nb === head) {
continue;
}
seen[nb] = 1;
stack.push(nb);
}
}
if (mark) {
mark.set(seen);
}
return hit;
}
interface Plan { next: number; path: number[]; rejected: number[]; trap: Uint8Array; chase: boolean; }
// 한 수를 정한다: 먹이까지 최단 경로 → (안전 검사) → 막히면 꼬리를 쫓는다
function planMove(g: Game, safeOn: boolean): Plan {
const b = g.b;
const head = g.body[0];
const tail = g.body[g.body.length - 1];
const plan: Plan = { next: -1, path: [], rejected: [], trap: new Uint8Array(b.n), chase: false };
const blocked = new Uint8Array(b.n);
for (let i = 0; i < g.body.length - 1; i += 1) {
blocked[g.body[i]] = 1;
}
if (g.food >= 0) {
const dist = distField(b, g.food, blocked, g.wrap);
const path = pathFrom(b, dist, head, g.wrap);
plan.path = path;
if (path.length > 0) {
if (!safeOn) {
plan.next = path[0];
return plan;
}
const v = simulate(g.body, path);
if (tailReachable(b, v, g.wrap, plan.trap)) {
plan.next = path[0];
return plan;
}
plan.rejected = path;
}
}
plan.chase = true;
const dist2 = distField(b, tail, blocked, g.wrap);
const nx = lowestNeighbor(b, dist2, head, g.wrap);
if (nx >= 0) {
plan.next = nx;
return plan;
}
for (let d = 0; d < 4; d += 1) {
const nb = neighborCell(b, head, d, g.wrap);
if (nb >= 0 && blocked[nb] === 0 && nb !== head) {
plan.next = nb;
return plan;
}
}
return plan;
}
// 칸 중심의 화면 좌표
function cellX(b: Board, i: number): number { return b.ox + ((i % b.cols) + 0.5) * b.cell; }
function cellY(b: Board, i: number): number { return b.oy + (Math.floor(i / b.cols) + 0.5) * b.cell; }
function wrapDelta(a: number, c: number, n: number, wrap: boolean): number {
let d = c - a;
if (wrap) {
if (d > n / 2) { d -= n; }
if (d < -n / 2) { d += n; }
}
return d;
}
// 마디 i 의 보간 위치 (칸 좌표). 지난 틱의 자리에서 이번 틱의 자리로 p(0~1) 만큼
function segPos(g: Game, i: number, p: number): [number, number] {
const b = g.b;
const cur = g.body[i];
const pv = i < g.prev.length ? g.prev[i] : cur;
const cx = cur % b.cols;
const cy = Math.floor(cur / b.cols);
const px = pv % b.cols;
const py = Math.floor(pv / b.cols);
return [px + wrapDelta(px, cx, b.cols, g.wrap) * p, py + wrapDelta(py, cy, b.rows, g.wrap) * p];
}
function drawTiles(ctx: CanvasRenderingContext2D, b: Board): void {
ctx.fillStyle = rgba(BG, 1);
ctx.fillRect(0, 0, W, H);
for (let y = 0; y < b.rows; y += 1) {
for (let x = 0; x < b.cols; x += 1) {
ctx.fillStyle = rgba((x + y) % 2 === 0 ? TILE_A : TILE_B, 1);
ctx.fillRect(b.ox + x * b.cell, b.oy + y * b.cell, b.cell + 0.5, b.cell + 0.5);
}
}
}
function drawFood(ctx: CanvasRenderingContext2D, b: Board, food: number, t: number): void {
if (food < 0) {
return;
}
const x = cellX(b, food);
const y = cellY(b, food);
const pulse = 0.5 + 0.5 * Math.sin(t * 0.12);
glow(ctx, x, y, b.cell * (1.3 + 0.35 * pulse), PINK, 0.55);
ctx.fillStyle = rgba(PINK, 1);
ctx.beginPath();
ctx.arc(x, y, b.cell * 0.3, 0, PI2);
ctx.fill();
ctx.fillStyle = rgba(CREAM, 0.9);
ctx.beginPath();
ctx.arc(x - b.cell * 0.08, y - b.cell * 0.09, b.cell * 0.09, 0, PI2);
ctx.fill();
}
function bodyColor(i: number, len: number): RGB {
return mix(MINT, SKY, len <= 1 ? 0 : i / (len - 1));
}
// 칸 중심 (x,y 칸 좌표, 소수 허용)에 마디 하나
function drawSeg(ctx: CanvasRenderingContext2D, b: Board, gx: number, gy: number, c: RGB, shrink: number): void {
const s = b.cell * (1 - shrink);
const cx = b.ox + (gx + 0.5) * b.cell;
const cy = b.oy + (gy + 0.5) * b.cell;
ctx.fillStyle = rgba(c, 1);
rrPath(ctx, cx - s / 2, cy - s / 2, s, s, s * 0.32);
ctx.fill();
}
function drawEyes(ctx: CanvasRenderingContext2D, b: Board, gx: number, gy: number, dirx: number, diry: number): void {
const cx = b.ox + (gx + 0.5) * b.cell;
const cy = b.oy + (gy + 0.5) * b.cell;
const px = -diry;
const py = dirx;
const r = b.cell * 0.09;
ctx.fillStyle = rgba(BG, 1);
for (let s = -1; s <= 1; s += 2) {
ctx.beginPath();
ctx.arc(cx + dirx * b.cell * 0.16 + px * s * b.cell * 0.18, cy + diry * b.cell * 0.16 + py * s * b.cell * 0.18, r, 0, PI2);
ctx.fill();
}
}
function headDir(g: Game): [number, number] {
if (g.body.length < 2) {
return [1, 0];
}
const b = g.b;
const dx = wrapDelta(g.body[1] % b.cols, g.body[0] % b.cols, b.cols, g.wrap);
const dy = wrapDelta(Math.floor(g.body[1] / b.cols), Math.floor(g.body[0] / b.cols), b.rows, g.wrap);
return [clamp(dx, -1, 1), clamp(dy, -1, 1)];
}
// 보간 없이 칸 그대로 그리는 기본 뱀
function drawSnakeCells(ctx: CanvasRenderingContext2D, g: Game, dim: number): void {
const len = g.body.length;
for (let i = len - 1; i >= 0; i -= 1) {
const c = g.body[i];
const col = mix(bodyColor(i, len), BG, dim);
drawSeg(ctx, g.b, c % g.b.cols, Math.floor(c / g.b.cols), col, 0.08);
}
const hd = headDir(g);
drawEyes(ctx, g.b, g.body[0] % g.b.cols, Math.floor(g.body[0] / g.b.cols), hd[0], hd[1]);
}
function start(root: HTMLElement, canvas: HTMLCanvasElement, statusEl: HTMLElement, btnEl: HTMLElement, make: Maker): () => void {
const ctx0 = canvas.getContext('2d');
if (!ctx0) {
return function (): void { return; };
}
const ctx: CanvasRenderingContext2D = ctx0;
const dpr = Math.min(window.devicePixelRatio || 1, 2);
canvas.width = Math.round(W * dpr);
canvas.height = Math.round(H * dpr);
ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
const reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
const inp: Input = { x: W / 2, y: H / 2, idle: 99999 };
const scene = make(inp, reduce);
let paused = false;
let rafId = 0;
let lastTs = -1;
let accMs = 0;
let lastLabel = '';
const cleaners: Array<() => void> = [];
function listen(target: EventTarget, type: string, fn: (e: Event) => void): void {
target.addEventListener(type, fn);
cleaners.push(function (): void { target.removeEventListener(type, fn); });
}
function show(): void {
scene.draw(ctx);
const t = scene.label();
if (t !== lastLabel) {
lastLabel = t;
statusEl.textContent = t;
}
}
function advance(ms: number): void {
const n = Math.round(ms / FIXED_DT);
for (let i = 0; i < n; i += 1) {
inp.idle += 1;
scene.step();
}
}
// 움직임 줄이기에서는 루프가 없으니 입력 직후 한 틱쯤 앞으로 보내 바로 그린다
function refresh(): void {
if (reduce) {
advance(FIXED_DT * 8);
show();
}
}
function toLocal(e: PointerEvent): void {
const r = canvas.getBoundingClientRect();
inp.x = clamp((e.clientX - r.left) * W / r.width, 0, W);
inp.y = clamp((e.clientY - r.top) * H / r.height, 0, H);
inp.idle = 0;
}
function tick(ts: number): void {
if (lastTs < 0) {
lastTs = ts;
}
const frameDt = Math.min(ts - lastTs, 160);
lastTs = ts;
if (!paused) {
accMs += frameDt;
while (accMs >= FIXED_DT) {
inp.idle += 1;
scene.step();
accMs -= FIXED_DT;
}
show();
}
rafId = requestAnimationFrame(tick);
}
btnEl.textContent = reduce ? BTN_NEXT : BTN_PAUSE;
if (reduce) {
root.classList.remove('is-demo');
advance(1400);
show();
}
listen(btnEl, 'click', function (): void {
if (reduce) {
advance(REDUCE_STEP_MS);
show();
return;
}
paused = !paused;
if (paused) {
root.classList.remove('is-demo');
} else {
root.classList.add('is-demo');
}
btnEl.textContent = paused ? BTN_PLAY : BTN_PAUSE;
});
listen(canvas, 'pointermove', function (e: Event): void {
toLocal(e as PointerEvent);
refresh();
});
listen(canvas, 'pointerdown', function (e: Event): void {
toLocal(e as PointerEvent);
scene.tap();
refresh();
});
listen(canvas, 'keydown', function (e: Event): void {
const k = (e as KeyboardEvent).key;
if (k === 'Enter' || k === ' ') {
e.preventDefault();
scene.tap();
refresh();
return;
}
// 이 장면이 쓰는 키만 막는다. 쓰지 않는 키(Tab 등)는 그대로 둔다
if (scene.key(k)) {
e.preventDefault();
refresh();
}
});
if (!reduce) {
rafId = requestAnimationFrame(tick);
}
return function (): void {
cancelAnimationFrame(rafId);
for (let i = 0; i < cleaners.length; i += 1) {
cleaners[i]();
}
};
}
const SEG_GAP = 9;
const SEG_COUNT = 26;
const SEG_MAX = 40;
const STEER_RATE = 0.075;
const FOLLOW_ITER = 4;
const FOLLOW_STIFF = 0.85;
const SPEED = 2.3;
const DAMP = 0.97;
const EAT_R = 11;
const WALL_PAD = 34;
const KEY_HOLD = 36;
const TRAIL_KEEP = 0.34;
const TXT_AUTO = '자동 조향';
const TXT_POINTER = '포인터를 쫓는 중';
const TXT_KEYS = '방향키 조종';
const TXT_LEN = '마디';
const TXT_SCORE = '먹이';
function makeScene(inp: Input, reduce: boolean): Scene {
const rnd = lcg(455404);
const px: number[] = [];
const py: number[] = [];
const qx: number[] = [];
const qy: number[] = [];
let ang = 0.3;
let fx = 0;
let fy = 0;
let t = 0;
let eaten = 0;
let keyAng = 0;
let keyLeft = 0;
let count = SEG_COUNT;
let painted = false;
function placeFoodAt(): void {
fx = 40 + rnd() * (W - 80);
fy = 36 + rnd() * (H - 72);
}
placeFoodAt();
for (let i = 0; i < SEG_MAX; i += 1) {
px.push(W * 0.3 - i * SEG_GAP);
py.push(H * 0.55);
qx.push(px[i]);
qy.push(py[i]);
}
function angDiff(a: number, c: number): number {
let d = c - a;
while (d > Math.PI) { d -= PI2; }
while (d < -Math.PI) { d += PI2; }
return d;
}
const scene: Scene = {
step(): void {
t += 1;
let goalX = fx;
let goalY = fy;
if (inp.idle < IDLE_TICKS) {
goalX = inp.x;
goalY = inp.y;
}
let want = Math.atan2(goalY - py[0], goalX - px[0]);
if (keyLeft > 0) {
keyLeft -= 1;
want = keyAng;
}
// 벽 가까이에서는 판 가운데 쪽으로 틀어 준다
if (px[0] < WALL_PAD || px[0] > W - WALL_PAD || py[0] < WALL_PAD || py[0] > H - WALL_PAD) {
want = Math.atan2(H / 2 - py[0], W / 2 - px[0]);
}
ang += clamp(angDiff(ang, want), -STEER_RATE, STEER_RATE) + Math.sin(t * 0.11) * 0.018;
// 머리만 직접 움직이고 나머지 마디는 이전 위치와의 차이(관성)로 나아간다
qx[0] = px[0];
qy[0] = py[0];
px[0] += Math.cos(ang) * SPEED;
py[0] += Math.sin(ang) * SPEED;
for (let i = 1; i < count; i += 1) {
const vx = (px[i] - qx[i]) * DAMP;
const vy = (py[i] - qy[i]) * DAMP;
qx[i] = px[i];
qy[i] = py[i];
px[i] += vx;
py[i] += vy;
}
// 거리 제약: 이웃 마디와의 간격을 SEG_GAP 으로 되돌린다
for (let it = 0; it < FOLLOW_ITER; it += 1) {
for (let i = 1; i < count; i += 1) {
const dx = px[i] - px[i - 1];
const dy = py[i] - py[i - 1];
const d = Math.sqrt(dx * dx + dy * dy) || 0.0001;
const k = ((d - SEG_GAP) / d) * FOLLOW_STIFF;
if (i === 1) {
px[i] -= dx * k;
py[i] -= dy * k;
} else {
px[i] -= dx * k * 0.5;
py[i] -= dy * k * 0.5;
px[i - 1] += dx * k * 0.5;
py[i - 1] += dy * k * 0.5;
}
}
}
const ex = px[0] - fx;
const ey = py[0] - fy;
if (ex * ex + ey * ey < EAT_R * EAT_R) {
eaten += 1;
if (count < SEG_MAX) {
count += 1;
px[count - 1] = px[count - 2];
py[count - 1] = py[count - 2];
qx[count - 1] = px[count - 1];
qy[count - 1] = py[count - 1];
}
placeFoodAt();
}
},
draw(ctx: CanvasRenderingContext2D): void {
// 배경을 반투명으로 덮어 지난 자리가 몇 프레임 남게 한다 (첫 프레임만 불투명)
ctx.fillStyle = rgba(BG, painted ? TRAIL_KEEP : 1);
ctx.fillRect(0, 0, W, H);
painted = true;
// 바닥 격자 — 칸 없는 판이라는 걸 보여 주려고 아주 옅게
ctx.strokeStyle = rgba(LILAC, 0.1);
ctx.lineWidth = 1;
for (let x = 0; x <= W; x += 30) {
ctx.beginPath();
ctx.moveTo(x, 0);
ctx.lineTo(x, H);
ctx.stroke();
}
for (let y = 0; y <= H; y += 30) {
ctx.beginPath();
ctx.moveTo(0, y);
ctx.lineTo(W, y);
ctx.stroke();
}
const pulse = 0.5 + 0.5 * Math.sin(t * 0.12);
glow(ctx, fx, fy, 22 + 6 * pulse, PINK, 0.6);
ctx.fillStyle = rgba(PINK, 1);
ctx.beginPath();
ctx.arc(fx, fy, 6.5, 0, PI2);
ctx.fill();
// 지난 자리 잔상 — 이전 위치(qx,qy)에서 지금 위치로 끄는 꼬리빛
for (let i = count - 1; i >= 0; i -= 1) {
const f = i / count;
const c = mix(MINT, SKY, f);
glow(ctx, qx[i], qy[i], 13 - 5 * f, c, 0.22);
}
for (let i = count - 1; i >= 0; i -= 1) {
const f = i / count;
const r = 6.4 - 3.4 * f;
ctx.fillStyle = rgba(mix(MINT, SKY, f), 1);
ctx.beginPath();
ctx.arc(px[i], py[i], r, 0, PI2);
ctx.fill();
}
ctx.fillStyle = rgba(BG, 1);
for (let s = -1; s <= 1; s += 2) {
ctx.beginPath();
ctx.arc(px[0] + Math.cos(ang) * 2.4 - Math.sin(ang) * s * 2.8, py[0] + Math.sin(ang) * 2.4 + Math.cos(ang) * s * 2.8, 1.3, 0, PI2);
ctx.fill();
}
},
label(): string {
const mode = keyLeft > 0 ? TXT_KEYS : (inp.idle < IDLE_TICKS ? TXT_POINTER : TXT_AUTO);
return mode + ' · ' + TXT_LEN + ' ' + count + ' · ' + TXT_SCORE + ' ' + eaten;
},
tap(): void {
placeFoodAt();
},
key(k: string): boolean {
if (k === 'ArrowLeft') { keyAng = Math.PI; }
else if (k === 'ArrowRight') { keyAng = 0; }
else if (k === 'ArrowUp') { keyAng = -Math.PI / 2; }
else if (k === 'ArrowDown') { keyAng = Math.PI / 2; }
else { return false; }
keyLeft = KEY_HOLD;
return true;
}
};
if (reduce) {
for (let i = 0; i < 60; i += 1) {
scene.step();
}
}
return scene;
}
export default function SkChainFollowRope() {
const rootRef = useRef<HTMLDivElement | null>(null);
const canvasRef = useRef<HTMLCanvasElement | null>(null);
const statusRef = useRef<HTMLParagraphElement | null>(null);
const btnRef = useRef<HTMLButtonElement | null>(null);
useEffect(() => {
const root = rootRef.current;
const canvas = canvasRef.current;
const statusEl = statusRef.current;
const btnEl = btnRef.current;
if (!root || !canvas || !statusEl || !btnEl) return;
return start(root, canvas, statusEl, btnEl, makeScene);
}, []);
return (
<main className={styles.stage}>
<div className={`${styles.sc} is-demo`} ref={rootRef}>
<canvas className={styles.sc__canvas} ref={canvasRef} width={480} height={300} tabIndex={0} aria-label="칸 없이 머리를 따라 거리 제약으로 끌려오는 사슬 몸통의 뱀" />
<p className={styles.sc__status} ref={statusRef} aria-live="polite">자동 조향</p>
<button className={styles.sc__btn} ref={btnRef} type="button">멈춤</button>
<p className={styles.sc__caption}>칸 없이 머리를 따라 거리 제약으로 끌려오는 사슬 몸통의 뱀</p>
</div>
</main>
);
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