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Played it on my phone, no keyboard so I got to admire the title screen. Looks good!

Notes for myself and anyone who wants to try the same: - emcc main.cpp -sUSE_SDL=2 -sUSE_SDL_IMAGE=2 --preload-file assets -o index.html builds - the main loop has to go. Browser doesn't let you block, so emscripten_set_main_loop(tick, 0, 1…

Went with index + generation number, so a stale handle gets detected instead of pointing at the wrong enemy. Works well. Thanks, and ferrous, no.

Fixes, in the order I'd try them: store an index or a handle in place of a pointer. std::deque if you only add at the ends, its references stay valid on push_back. Calling reserve() up front hides the bug until you exceed it.

Say it louder.

Yes. push_back reallocates when it runs out of capacity, and all your pointers point into the old buffer. It's the same reason Rust refuses the code in tomasz's thread, /progrider/t/AhtK41Hy5_6g, except here it compiles and you get to find …

std::vector<Entity> entities; and the enemies keep an Entity* target. After some spawns, target points to garbage, and it crashes only sometimes. Valgrind says invalid read. Is it because vector moved?

Yes, _physics_process runs at a fixed rate, and newer versions have physics interpolation you switch on in the project settings. Solved, thanks jf.

Is this what Godot does with its physics tick?

Read the article. Jump heights are identical now. I'm clamping frame_time to 0.25s as well, otherwise dragging the window gives a spiral of updates.

Variable dt makes the integration depend on the frame rate. Fixed step with an accumulator: accumulator += frame_time; while (accumulator >= STEP) { update(STEP); accumulator -= STEP; } render(accumulator / STEP); Pass the leftover fraction…

Small 2D platformer in C++ with SDL. I multiply velocity by dt every frame. At steady 60 it's smooth. When it dips, the player stutters and jumps come out at a different height, which breaks some levels.