:root {
    --font-sans:
        ui-sans-serif,
        system-ui,
        -apple-system,
        BlinkMacSystemFont,
        "Segoe UI",
        sans-serif;

    --color-page: #f3f6fb;
    --color-surface: #ffffff;
    --color-surface-soft: #f7f9fd;
    --color-surface-dark: #15243c;

    --color-text: #223750;
    --color-muted: #6d7f96;
    --color-muted-strong: #344763;
    --color-border: #e4ebf5;

    --color-primary: #536ce6;
    --color-primary-hover: #435cce;
    --color-primary-soft: #edf2ff;
    --color-primary-border: #dbe4ff;

    --color-success: #166534;
    --color-success-bg: #ecfdf5;
    --color-success-border: #bbf7d0;

    --color-warning: #92400e;
    --color-warning-bg: #fffbeb;
    --color-warning-border: #fde68a;

    --color-danger: #991b1b;
    --color-danger-bg: #fef2f2;
    --color-danger-border: #fecaca;
    --color-danger-button: #dc2626;
    --color-danger-button-hover: #b91c1c;

    --radius-md: 10px;
    --radius-lg: 14px;
    --radius-xl: 18px;
    --radius-full: 999px;

    --shadow-sm: 0 5px 16px rgba(31, 53, 90, 0.04);
    --shadow-md: 0 15px 38px rgba(26, 51, 82, 0.055);

    --layout-max-width: 1900px;
    --input-height: 44px;

    /* V2.1-A: native controls, always a light blue-grey, never a dark menu. */
    --color-control: #f7f9fd;
    --color-control-hover: #edf2fa;
    --color-control-border: #dbe4f1;
    --color-control-hover-border: #becbe0;
    --color-control-focus: #8296ea;
    --color-control-disabled: #f1f3f8;
    --color-control-option: #ffffff;
    --color-control-ink: #344763;
    --color-card-shadow: 0 15px 38px rgba(26, 51, 82, 0.055);
    --radius-card: 18px;
    --workspace-card-gap: 19px;

    /* V2.1-B: subtle status surfaces shared by dashboard and mobile cards.
       Calendar appointments continue to derive their accent from lesson type. */
    --lesson-status-scheduled-accent: #617cf0;
    --lesson-status-scheduled-surface: #edf2ff;
    --lesson-status-completed-accent: #12a58b;
    --lesson-status-completed-surface: #eaf8f4;
    --lesson-status-cancelled-accent: #ce706c;
    --lesson-status-cancelled-surface: #fff0ee;
    --lesson-status-no-show-accent: #c28a36;
    --lesson-status-no-show-surface: #fff5e8;
    --button-height: 44px;
}

* {
    box-sizing: border-box;
}

html {
    min-height: 100%;
    background: var(--color-page);
}

body {
    min-height: 100%;
    margin: 0;
    font-family: var(--font-sans);
    background: var(--color-page);
    color: var(--color-text);
    -webkit-font-smoothing: antialiased;
    text-rendering: optimizeLegibility;
}

header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 30px;
    min-height: 72px;
    background: var(--color-surface);
    color: var(--color-text);
    padding: 12px 40px;
    border-bottom: 1px solid var(--color-border);
}

header h1 {
    display: inline-flex;
    align-items: center;
    flex: 0 0 auto;
    gap: 11px;
    margin: 0;
    color: var(--color-text);
    font-size: 18px;
    font-weight: 750;
    line-height: 1.2;
    letter-spacing: -0.035em;
    white-space: nowrap;
}

header h1::before {
    content: "F";
    display: grid;
    place-items: center;
    flex: 0 0 36px;
    width: 36px;
    height: 36px;
    border-radius: 11px;
    background: var(--color-primary);
    color: #ffffff;
    font-size: 20px;
    font-weight: 800;
}

nav {
    display: flex;
    flex: 1 1 auto;
    flex-wrap: wrap;
    justify-content: flex-end;
    align-items: center;
    gap: 8px;
}

nav a,
.nav-logout-button {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-height: 40px;
    color: var(--color-muted-strong);
    text-decoration: none;
    background: transparent;
    border: 1px solid transparent;
    padding: 8px 12px;
    border-radius: 9px;
    font-weight: 600;
    font-size: 13px;
    transition: background 0.15s ease, color 0.15s ease;
}

nav a:hover,
.nav-logout-button:hover {
    background: var(--color-surface-soft);
    color: var(--color-text);
}

.nav-logout-button {
    min-height: 40px;
    border-color: var(--color-border);
    color: var(--color-muted);
}

nav a.active,
nav a.active:hover {
    background: var(--color-primary-soft);
    color: var(--color-primary-hover);
    font-weight: 750;
}

main {
    max-width: var(--layout-max-width);
    margin: 30px auto;
    padding: 0 32px;
}

section {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-xl);
    padding: 24px;
    margin-bottom: 20px;
    box-shadow: var(--shadow-sm);
}

h1,
h2,
h3 {
    color: var(--color-text);
    letter-spacing: -0.02em;
}

h2,
h3 {
    margin-top: 0;
}

p {
    line-height: 1.55;
}

form {
    display: grid;
    gap: 16px;
    max-width: 520px;
}

.nav-logout-form {
    display: inline-flex;
    gap: 0;

    max-width: none;
    margin: 0;
}

label {
    display: block;
    font-weight: 600;
    margin-bottom: 6px;
    color: var(--color-text);
}

input,
select,
textarea {
    width: 100%;
    min-height: var(--input-height);
    padding: 10px 12px;
    border: 1px solid var(--color-control-border);
    border-radius: var(--radius-md);
    background: var(--color-surface);
    color: var(--color-control-ink);
    font-family: inherit;
    font-size: 15px;
    line-height: 1.4;
    outline: none;
    transition:
        border-color 0.15s ease,
        box-shadow 0.15s ease,
        background 0.15s ease;
}

input:not(:disabled):not([type="checkbox"]):not([type="radio"]):not([type="color"]):not([type="file"]):not([type="search"]):hover,
select:not(:disabled):hover,
textarea:not(:disabled):hover {
    border-color: var(--color-control-hover-border);
    background-color: var(--color-control-hover);
}

input::placeholder,
textarea::placeholder {
    color: #9ca3af;
    opacity: 1;
}

/* Exclude native checkbox, radio, colour and file widgets from tinted surfaces. */
input:not([type="hidden"]):not([type="checkbox"]):not([type="radio"]):not([type="color"]):not([type="file"]),
select, textarea {
    background-color: var(--color-control);
}

select {
    cursor: pointer;
    color-scheme: light;
}
/* The expanded native popup is browser/OS controlled; these colours are hints. */
select option,
select optgroup {
    background-color: var(--color-control-option);
    color: var(--color-control-ink);
}

input:focus,
select:focus,
textarea:focus {
    border-color: var(--color-control-focus);
    box-shadow: 0 0 0 3px rgba(83, 108, 230, 0.14);
}

input:not([type="hidden"]):not([type="checkbox"]):not([type="radio"]):not([type="color"]):not([type="file"]):focus,
select:focus, textarea:focus {
    background-color: #ffffff;
}

textarea {
    min-height: 120px;
    resize: vertical;
    line-height: 1.55;
}

input[type="file"] {
    padding: 6px 8px;
    cursor: pointer;
}

input[type="file"]::file-selector-button {
    margin-right: 10px;
    border: 0;
    border-radius: 8px;
    background: var(--color-surface-soft);
    color: var(--color-muted-strong);
    padding: 8px 10px;
    font-family: inherit;
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
}

input[type="file"]::file-selector-button:hover {
    background: #f3f4f6;
}

input[type="color"] {
    width: 56px;
    min-width: 56px;
    height: var(--input-height);
    padding: 4px;
    cursor: pointer;
}

input[type="color"]::-webkit-color-swatch-wrapper {
    padding: 0;
}

input[type="color"]::-webkit-color-swatch {
    border: none;
    border-radius: 8px;
}

input[disabled],
select[disabled],
textarea[disabled] {
    background: var(--color-control-disabled);
    color: #8291a7;
    cursor: not-allowed;
}

button {
    min-height: var(--button-height);
    border: none;
    background: var(--color-primary);
    color: white;
    padding: 10px 14px;
    border-radius: var(--radius-md);
    cursor: pointer;
    font-weight: 700;
    font-size: 14px;
    transition: background 0.15s ease, transform 0.12s ease, box-shadow 0.15s ease;
}

button:hover {
    background: var(--color-primary-hover);
}

button:not(:disabled):active {
    transform: translateY(1px);
}

button:disabled {
    opacity: 0.55;
    cursor: not-allowed;
    transform: none;
    pointer-events: none;
}

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

button:focus-visible,
a:focus-visible,
input:focus-visible,
select:focus-visible,
textarea:focus-visible {
    outline: 3px solid #355de8;
    outline-offset: 2px;
}

ul {
    padding-left: 20px;
}

li {
    margin-bottom: 10px;
}

.dashboard-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(190px, 1fr));
    gap: 16px;
}

.dashboard-card strong {
    display: block;
    margin-top: 0;
    color: var(--color-text);
    font-size: 32px;
    font-weight: 700;
    line-height: 1;
    letter-spacing: -0.04em;
}

.danger-button {
    background: var(--color-surface);
    color: var(--color-danger-button);
    border: 1px solid var(--color-danger-border);
}

.danger-button:hover {
    background: var(--color-danger-bg);
    color: var(--color-danger-button-hover);
    border-color: var(--color-danger-button);
}

.secondary-button {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-height: var(--button-height);
    padding: 10px 14px;
    border: 1px solid #ccd5e3;
    border-radius: var(--radius-md);
    background: var(--color-surface);
    color: var(--color-muted-strong);
    text-decoration: none;
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    transition:
        background 0.15s ease,
        border-color 0.15s ease,
        color 0.15s ease,
        transform 0.12s ease,
        box-shadow 0.15s ease;
}

.secondary-button:active {
    transform: translateY(1px);
}

.secondary-button:hover {
    background: var(--color-surface-soft);
    border-color: #9ca3af;
    color: var(--color-text);
}

@media (max-width: 1100px) {
    header {
        flex-direction: column;
        align-items: flex-start;
        gap: 14px;
    }

    nav {
        width: 100%;
        justify-content: flex-start;
    }
}

@media (max-width: 900px) {
    header {
        padding: 16px;
    }

    header h1 {
        font-size: 20px;
    }

    main {
        margin: 16px auto;
        padding: 0 16px;
    }

    section {
        padding: 18px;
        border-radius: var(--radius-lg);
    }

    nav {
        gap: 8px;
    }

    nav a {
        flex: 1 1 auto;
        min-width: 120px;
    }
}

@media (max-width: 560px) {
    main {
        padding: 0 12px;
    }
}