/* CSS viet tay, khong framework: giao dien nay ton tai de quay demo, khong de canh
   tranh voi mot san pham that. */

:root {
    --nen: #14161a;
    --the: #1e2128;
    --vien: #2c313b;
    --chu: #e6e8ec;
    --chu-mo: #9aa1ad;
    --nhan: #4f8cff;

    --ghe-trong: #2f3742;
    --ghe-nguoi-khac: #6b4a1f;
    --ghe-da-ban: #4a2a2a;
    --ghe-cua-toi: #1f6b3a;
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    background: var(--nen);
    color: var(--chu);
    font: 15px/1.5 system-ui, "Segoe UI", sans-serif;
}

header {
    display: flex;
    align-items: baseline;
    gap: 1rem;
    padding: 1rem 1.5rem;
    border-bottom: 1px solid var(--vien);
}

header h1 {
    margin: 0;
    font-size: 1.1rem;
    letter-spacing: 0.02em;
}

#nguoi-dung {
    margin-left: auto;
    color: var(--chu-mo);
    font-size: 0.9rem;
}

main {
    max-width: 900px;
    margin: 0 auto;
    padding: 1.5rem;
}

.dang-tai,
.trong {
    color: var(--chu-mo);
}

.the {
    background: var(--the);
    border: 1px solid var(--vien);
    border-radius: 8px;
    padding: 1rem;
    margin-bottom: 0.75rem;
}

label {
    display: block;
    margin: 0.75rem 0 0.25rem;
    color: var(--chu-mo);
    font-size: 0.85rem;
}

input {
    width: 100%;
    padding: 0.55rem 0.7rem;
    background: var(--nen);
    border: 1px solid var(--vien);
    border-radius: 6px;
    color: var(--chu);
    font: inherit;
}

button {
    padding: 0.55rem 1rem;
    background: var(--nhan);
    border: 0;
    border-radius: 6px;
    color: #fff;
    font: inherit;
    cursor: pointer;
}

button.phu {
    background: transparent;
    border: 1px solid var(--vien);
    color: var(--chu);
}

button:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.loi {
    margin: 0.75rem 0;
    padding: 0.6rem 0.8rem;
    background: #3a1f1f;
    border-left: 3px solid #b45252;
    border-radius: 4px;
}

/* --- So do ghe (Task 3) --- */

.hang {
    display: flex;
    align-items: center;
    gap: 0.35rem;
    margin-bottom: 0.35rem;
}

.ten-hang {
    width: 1.5rem;
    color: var(--chu-mo);
    font-size: 0.8rem;
}

.ghe {
    width: 2rem;
    height: 2rem;
    border: 0;
    border-radius: 4px;
    background: var(--ghe-trong);
    color: var(--chu);
    font-size: 0.75rem;
    cursor: pointer;
}

.ghe.nguoi-khac-giu {
    background: var(--ghe-nguoi-khac);
    cursor: not-allowed;
}

.ghe.da-ban {
    background: var(--ghe-da-ban);
    cursor: not-allowed;
}

.ghe.cua-toi {
    background: var(--ghe-cua-toi);
}

.ghe.vua-doi {
    animation: nhay 0.6s ease-out;
}

@keyframes nhay {
    from {
        outline: 2px solid var(--nhan);
    }
    to {
        outline: 2px solid transparent;
    }
}

/* --- Man hinh, chu thich va thanh hanh dong --- */

.man-hinh {
    max-width: 22rem;
    margin: 0 auto 1.5rem;
    padding: 0.35rem;
    background: var(--vien);
    border-radius: 0 0 40% 40%;
    color: var(--chu-mo);
    font-size: 0.75rem;
    text-align: center;
}

.chu-thich {
    display: flex;
    gap: 1rem;
    margin: 1rem 0;
    color: var(--chu-mo);
    font-size: 0.8rem;
}

.chu-thich span::before {
    content: '';
    display: inline-block;
    width: 0.8rem;
    height: 0.8rem;
    margin-right: 0.35rem;
    border-radius: 3px;
    vertical-align: -1px;
}

.chu-thich .k-trong::before { background: var(--ghe-trong); }
.chu-thich .k-nguoi-khac::before { background: var(--ghe-nguoi-khac); }
.chu-thich .k-da-ban::before { background: var(--ghe-da-ban); }
.chu-thich .k-cua-toi::before { background: var(--ghe-cua-toi); }

.thanh-hanh-dong {
    position: sticky;
    bottom: 0;
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 0.9rem 1rem;
    background: var(--the);
    border: 1px solid var(--vien);
    border-radius: 8px;
}

.dem-nguoc {
    font-variant-numeric: tabular-nums;
    font-size: 1.1rem;
}

.dem-nguoc.gap {
    color: #ff8f6b;
}

a {
    color: var(--nhan);
}

header h1 a {
    color: inherit;
    text-decoration: none;
}